CREW TRAINING – NAVIGATION – SEPTEMBER 6, 2007



CREW TRAINING – NAVIGATION

Overview

What’s the problem with Navigation?

Flat charts – round earth

North – not where we say it is

CHARTS

|For the purpose of coastal navigation, the earth is considered to be a perfect sphere. To represent the features of the earth’s |

|spherical surface on the flat surface of a chart, a process termed “projection” is used. Two basic types of projection used in |

|making piloting charts are Mercator and Polyconic. For the purposes of this course, we will be concerned with Mercator projections|

|only. |

|Mercator Projection |Mercator charts are the primary charts used aboard boats. A Mercator projection is made by |

| |transferring the surface of the globe (representing the earth) onto a cylinder. |

| | |

| |The distinguishing feature of the Mercator projection is that the meridians are projected so|

| |they appear to be equal distance from each other and parallel. |

GENERAL INFORMATION BLOCK (Title Block)

The general information block contains the following items:

• The unit of depth measurement, listed as soundings (feet, meters or fathoms).

• The chart title which is usually the name of the prominent navigable body of water within the area covered in the chart.

• A statement of the type of projection and the scale.

CHART SCALES

The scale of a nautical chart is the ratio comparing a unit of distance on the chart to the actual distance on the surface of the earth.

For example: The scale of 1:5,000,000 means that one of some kind of measurement of the chart is equal to 5,000,000 of the same kind of measurement on the earth's surface. One inch on the chart would equal 5,000,000 inches on the earth’s surface. This would be a small scale chart, since the ratio 1/5,000,000 is a very small number. A large scale chart represents a smaller area than that of a small scale chart.

Remember – think opposite!

Large Scale Charts = small area – lots of detail ~ 1:10,000

Small Scale Charts = large area – less detail ~ 1:500,000

SOUNDINGS – DEPTH CURVES

Soundings =

Depth of the water at low tide (mean low water or mean low lower water) + the characteristic of the bottom

This is accomplished through the use of combinations of numbers, color codes, underwater contour lines, and a system of symbols and abbreviations.

Depth of water may be charted in feet, meters or fathoms (a fathom equals six feet). The chart legend will indicate which unit (feet, meters or fathoms) is used. Make sure you check and are sure which measurement is being used!

DEPTH SOUNDINGS

|Generally, shallow water is tinted darker blue on a chart, while deeper water is tinted light blue or white. |

Contour lines, also called fathom curves, connect points of roughly equal depth and provide a profile of the bottom.

VERTICAL CLEARANCES – BRIDGES/LANDMARKS

Heights of landmarks are given in feet above sea level.

Vertical clearances of bridges are given in feet from mean high water

What is the vertical clearance for the swing rr bridge connecting Aquidenck Island with the mainland of Rhode Island?

SYMBOLS

Many symbols and abbreviations are used on charts. It is a quick way to determine the physical characteristics of the charted area and information on ATONS. These symbols are uniform and standardized, but may vary depending on the scale of the chart or chart series. These standardized chart symbols and abbreviations are shown in the Pamphlet ‘CHART No. 1 ~ and are also shown on the back of your training chart!

Nautical purple ink (magenta) is used for most information since it is easier to read under red light normally used for navigating at night.

Slanted Lettering denotes features affected by tide or current (ATONS)

Straight Lettering denotes features unaffected by the tide (LIGHTHOUSE)

ATONS (Buoys)

The basic symbol for a buoy is a diamond and small circle.

• A dot will be shown instead of the circle on older charts.

• The diamond may be above, below or alongside the circle or dot.

• The small circle or dot denotes the approximate position of the buoy mooring.

• The diamond is used to draw attention to the position of the circle or dot and to describe the aid.

LIGHTHOUSES

The basic symbol is a black dot with a magenta “flare” giving much the appearance of a large exclamation mark (!). Major lights are named and described; minor lights are described only.

Find Buzzards Bay Lighthouse

LANDMARKS

Prominent landmarks, such as water towers, smoke stacks, and flagpoles, are pinpointed by a standard symbol of a dot surrounded by a circle. A notation next to the symbol defines the landmark’s nature. The omission of the dot indicates the location of the landmark is only an approximation.

Find the Radar Tower in Martha’s Vineyard

WRECKS/ROCKS/REEFS

These are marked with standardized symbols, for example, a sunken wreck may be shown either by a symbol or by an abbreviation plus a number that gives the wreck's depth at mean low or lower low water. A dotted line around any symbol calls special attention to its hazardous nature.

End of 1st Class

Circles/Degrees and Minutes

GREAT CIRCLES – always pass through center of the earth

divides earth into two equal parts

Example – Equator

Any Circle that passes through the N & S poles

CIRCLES – there are 360 degrees in a circle –

a great circle is no different

Degrees are written like this 40°

Degrees – there are 60 minutes in every degree

Minutes are written like this 15’

Minutes are always expressed in two digits

Thus – nine minutes is written as 09’

Minutes - Who can tell me what the next division would be?

Each minute has 60 seconds

Seconds are written like this 25”

Seconds, like minutes are expressed as two digits

Six Seconds is written as 06”

IN MODERN NAVIGATION – SECONDS ARE RARELY USED

INSTEAD, MINUTES ARE EXPRESSED IN TENTHS

THUS – Forty Degrees, Fifteen minutes, Twelve Seconds

Is written as:

40° 15.2’

12 = 12/60 = .2

PARALLALS OF LATITUDE (Abbreviated “L”)

Parallels are circles on the surface of the earth moving from the equator to the North or South Pole. They are parallel to the equator and known as parallels of latitude, or just latitude.

|Parallels of equal latitude run in a west and east direction (left and right on a chart). They are measured in degrees, minutes, and seconds, |

|(OR TENTHS) in a north and south direction, from the equator. (0° at the equator to 90° at each pole). |

| |

|The Equator is 0° |

|The North Pole is 90° north latitude, |

|The South Pole is 90° south latitude. |

| |

|We are at approximately 42° - THIS IS WRITTEN AS N 42° |

| |

|The equator itself is a special parallel because it is also a great circle. |

| |

|One degree of latitude is equal to 60 nautical miles (NM) |

| |

|One minute of latitude is equal to 1 NM. |

| |

| |

|Latitude scales, are indicated along the side margins of charts by divisions along the black-and-white border in the left and the right margins.|

| |

|REMEMBER – One degree of Latitude = 60 NM |

|One Minute of Latitude = 1 NM |

| |

| |

| |

|You can always measure distance by using the LATITUDE SCALE |

|ON THE RIGHT OR LEFT SIDE OF THE CHART |

| |

|Always use the latitude scale to measure distance in navigation. |

|A degree of latitude is measured up or down. |

| |

| |

| |

| |

MERIDIANS of longitude “LONGitude” (Abbreviated “Lo”)

Meridians of longitude are also great circles

Prime meridian 000°

Greenwich England – separates East/West

From this point – Longitude is measured both east & west for 180°

International Date Line = 180th Meridian

Meridians are not parallel – They converge at the poles!

|Meridians of Longitude run in a north and south direction (top to bottom on a chart) and are measured in degrees, minutes, and seconds (or |

|tenths), in an east or west direction. |

LONGITUDE SCALE IS ON THE TOP AND BOTTOM OF THE CHART

Only the latitude scale is used for measuring distance!

Why???

Because the world is round and charts are flat . . .

|Longitude is always expressed in three digits – thus SEVENTY TWO DEGREES WEST is expressed as W 072° |

| |

| |

|PRACTICE PROBLEMS: |

|Find the Latitude/Longitude for the following: |

| |

|A. “2” Buoy south of Point Judith: Latitude: _ _° _ _._ ‘ N/S Longitude: _ _ _ ° _ _. _ ‘ W/E |

| |

|B. Green Bell “1B1” north of Block Island: L: _ _° _ _._’ N/S Lo: _ _ _ ° _ _. _ ‘ W/E |

| |

|C. Brenton Reef (Horn): L: _ _° _ _._ N/S Lo: _ _ _ ° _ _. _ W/E |

| |

|D. Buzzards Bay Horn: L: ____________________ Lo: ____________________ |

| |

|E. Red Buoy “VS” (SE of Cuttyhunk) L: _______________ Lo: _______________ |

| |

|F. Green Buoy “29” (E of Gay Head): L: _____________ Lo: _______________ |

| |

|G. Black & White “VS” Whistle: L: _______________ Lo: ________________ |

| |

|H. Green Buoy “1” (W of Nomans Land): L: ___________ Lo: ________________ |

| |

|End of Class #2 |

COMPASS ROSE

|Nautical charts usually have one or more compass roses printed on them. |

|These are similar in appearance to the compass card and, like the compass card, are oriented with north at the top. |

| |

|Directions on the chart are measured by using the compass rose. |

| |

|Direction is measured as a straight line from the center point of the circle to a number on the compass rose. |

| |

|The outer ring represents “true” directions |

|The inner ring represents “magnetic” directions. |

| |

|How many are on the TR Chart? |

| |

|ALWAYS USE THE COMPASS ROSE CLOSEST TO YOUR CURRENT POSITION |

|We will discuss the difference soon |

THE COMPASS

|The magnetic compass, even though it has been around for a long time, is still very important for safely navigating a boat. Whether steering a |

|course out of sight of landmarks or in poor visibility, the magnetic compass is the primary tool for guiding the boat to its destination. |

The compass consists of a “compass card” mounted on a pin of sorts. The compass card is divided into 360 degrees and is numbered all the way around. A magnet is attached to the compass card that is attracted to the magnetic field around it. Ideally it points to the earth’s magnetic north pole. Zero on the compass card is in line with the magnet attached to the card. When the boat turns, the magnet continues to point north - The compass card therefore stays stationary and the boat turns around it!

In an ideal world, the compass would point towards the north as indicated on our charts… as we know – our world is not ideal, and this leads us to the second problem with navigation!

VARIATION AND DEVIATION

Variation

The North Pole is not where it is supposed to be!

In fact it moves around! And not only does it move around – but it appears differently in different places!

We call this difference – VARIATION ~ Variation can be easterly or westerly

Remember the two rings on the Compass Rose – the Inner Ring represents what our compass should point to as magnetic north.

True vs Magnetic

Directions measured on a chart are in true degrees or magnetic degrees as follows:

• True direction uses the North Pole as a reference point.

• True direction differs from magnetic direction by variation.

• Directions steered by the compass on the boat are magnetic degrees.

The Compass Rose will tell you what the Variation is in the area where you are navigating – It also tells you what the annual increase in variation is.

Always use the Compass Rose closest to your position!

Deviation

So – we have a magnet in the compass on the boat . . . guess what – it is not alone! There are many other magnetic fields on the boat – your radio, the metal steering wheel, radio speakers etc. These magnetic fields cause the compass to be inaccurate. Compasses are corrected for these fields, but no amount of correcting can make them totally accurate. This error is referred to as deviation.

Compasses can (and most do) have different errors on different headings!

A deviation table is constructed to determine the error on different headings.

Deviation can be easterly or westerly

Thankfully, the method of creating a deviation table is beyond the scope of this review!

You must know however, how to convert true courses to magnetic, and magnetic courses to true courses.

TO “UNCORRECT” ie. go from True course to compass course:

TRUE = TRUE COURSE = 300˚ True

VIRGINS = VARIATION + 15˚W

MAKE = MAGNETIC = 315˚ Magnetic

DULL = DEVIATION - 05˚E

COMPANIONS = COMPASS = 310˚ Compass

AT = ADD

WEDDINGS = WEST

TO CORRECT ie. Go from Compass course to True FLIP the formula

Or some folk say:

CAN = COMPASS = 310˚ psc

DEAD = DEVIATION + 05˚E

MEN = MAGNETIC = 315˚ Magnetic

VOTE = VARIATION - 15˚W

TWICE = TRUE = 300˚ True

AT = ADD

ELECTIONS = EAST

FOR YOUR CREW SIGN OFF – YOU WILL NEED ONLY TO PLOT A MAGNETIC COURSE – YOU WILL NOT HAVE TO CONVERT TO COMPASS

[pic]

TO “UNCORRECT” ie. go from True course to compass course:

TRUE = TRUE COURSE = 35˚

VIRGINS = VARIATION + 10W

MAKE = MAGNETIC = 45 Magnetic

DULL = DEVIATION - 5E

COMPAINIONS = COMPASS COURSE = 40˚ psc

AT = ADD

WEDDINGS = WEST

For the following problems – Variation is 15° W

Deviation is 2° E (on all courses)

Your true heading is 100°

Your Magnetic heading is: ______

Your compass heading is: ______

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Your true heading is 240°

Your Magnetic heading is: ______

Your compass heading is: ______

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Your true heading is 120°

Your Magnetic heading is: ______

Your compass heading is: ______

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Your compass heading is 350°

Your Magnetic heading is: ______

Your true heading is: ______

Your compass heading is 215°

Your Magnetic heading is: ______

Your true heading is: ______

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Your compass heading is 320°

Your Magnetic heading is: ______

Your true heading is: ______

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Your compass heading is 115°

Your Magnetic heading is: ______

Your true heading is: ______

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Your compass heading is 123°

Your Magnetic heading is: ______

Your true heading is: ______

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Your compass heading is 355°

Your Magnetic heading is: ______

Your true heading is: ______

MORE . . .

From page 8 above:

A. What is the magnetic course from Green Buoy “1B1” to Red Buoy “2”?

a. What is the true course?

b. What is the distance between the two marks?

B. What is the true course from Red Buoy “2” to Green Buoy “1B1”?

C. What is the true course from R “2” to White Buoy “A”?

a. What is the magnetic course?

b. What is the distance between the two marks?

D. What is the true course from White Buoy W or “A” to R “2”?

E. What is the magnetic course from Buoy W or “A” to Green Buoy “1B1”?

a. What is the true course?

b. What is the distance between the two marks?

F. What is the magnetic course from RB “VS” to Green Buoy “29”?

G. What is the true course from GB “29” to RB “VS”?

a. What is the distance between the two?

H. What is the true course from GB “29” to BW “VS” whistle?

a. What is the distance between the two?

I. What is the magnetic course from BW “VS” Whistle to RB “VS” Whistle?

a. What is the distance between the two?

J. What is the magnetic course from BW “VS” Whistle to Green Buoy “1” (E of Nomans Land)?

a. What is the distance between the two?

End of Class #3

We are almost done . . .

Computation of Speed/Time and Distance:

Speed, time and distance are critical elements in navigation. All three are interrelated in the way they are calculated.

If you think back to 5th Grade, you know that

S x T = D

We can express this formula in a “magic circle”

Cover up the element you want to find – use the resulting formula

For example:

To find DISTANCE – multiply speed times time S x T = D

To find SPEED – divide distance by time D = S

T

To find TIME – Divide distance by speed D = T

S

UNITS OF MEASUREMENT

Using the above formula the units of measurement are:

Distance – Nautical Miles (NM)

Speed - Knots

Time – in hours

TIME is perhaps the most confusing.

Calculations of time

We use military time in the Auxiliary

So 1:00 pm = 1300 hrs and so on

Nothing much to converting military time to civilian time –

If the am – do nothing 9:00 am = 0900 hrs

For the pm – add or subtract 12

So . . . 1:00 pm = 1300 hrs

2:00 pm = 1400 hrs

1500 hrs = 3:00 pm

2400 hrs = 12 midnight

The difficulty arises when subtracting one time from another to determine an interval of time:

2300

-1800

500 – or 5 hours . . . not so bad, but

1300

- 1243

Hmmmmm well 43 from 100 = 57 – but that can’t be right . . .

To do this problem – first convert 1300 to 1200 + 60 minutes or 1260

Now subtracting 1243 becomes easy . . . - 1243

17

Ok – now you try some:

1452 1534 0259 0423 1945

- 1249 - 0219 - 0145 - 0319 - 1816

Now they will get harder:

0945 0836 1016 0555 0830

- 0352 - 0647 - 0827 -0359 - 0645

When you use the formula above – you will always end up with hours

There are 2 ways to convert hours into minutes and vice versa

First – know these:

There are 60 minutes in one hour

Half an hour = 30 minutes or .5 hours

15 minutes = ¼ hour or .25 hours

45 minutes = ¾ hour or _____ hours

6 minutes = .10 hours

12 minutes = ______

15 minutes = .25 hours

18 minutes = .3 hours

24 minutes = _____ hours

30 minutes = ______ hours

36 minutes = .6 hours

42 minutes = .7 hours

45 minutes = _______ hours [ 45/60=.75]

48 minutes = .8 hours

54 minutes = .9 hours [54/60 = .9]

60 minutes = ______ hours

Now lets try it in reverse:

{ no cheating and looking at the preceding page!}

1.0 hours = 60 minutes

.9 hours = 54 minutes

.8 hours = 48 minutes

.75 hours = ____________ do this in your head!

.7 hours = ______ minutes

.6 hours = _______ minutes

.5 hours = ________ minutes (another easy one!)

.4 hours = 24 minutes

.3 hour = 18 minutes

.25 hours = _________ minutes (get this one!)

.2 hours = __________ minutes

.1 hour = ___________ minutes

Ready to try some?

1500 1256 1525 1329 0936 0745

-1312 -1150 - 1231 -1259 - 0836 -0727

Now – convert your answers to hours:

______ ______ ______ ______ ______ ______

OK – now to use our “magic circle”

Find Distance:

Speed = 10 kts

S x T = D 10 x 5 = 50 D = 50 NM

Time = 5 hours

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Speed = 3 kts

S x T = D 3 x 2.5 = 7.5 D = 7.5 NM

Time = 2.5 hours

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On your own:

Find Distance:

S = 8 kts

T = .3 hours

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S = 10 kts

T = 15 minutes

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S = 15 kts

T = 1 hour

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S = 5 kts

T = 30 minutes

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S = 3 kts

T = 42 minutes

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S = 7 kts Remember to find hours

Divide minutes by 60

T = 40 minutes

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S = 15 kts

T = 10 minutes

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S = 12 kts

T = 90 minutes

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S = 17 kts

T = 15 mins

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One more . . S = 18.5 kts T = 6 minutes D =

Find Speed:

D = 45

T = 1.5 hours

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D = 30

T = 90 minutes

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D = 12

T = 1 hr 45 minutes

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D = 5

T = 1 hour

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D = 10

T = .10 hour

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D = 7

T = 12 minutes

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D = 15

T = 45 minutes

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D = 25

T = 2 hours 12 minutes

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D = 3

T = 1 hour 35 minutes

Find time – convert all time to hours and minutes

D = 17 NM

S = 17 kts

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D = 15 NM

S = 2 kts

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D = 25 NM

S = 7.5 kts

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D = 19 NM

S = 1 kt

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D = 27 NM

S = 9 kts

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D = 2 NM

S = 5 kts

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D = 5 NM

S = 2.5 kts

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D = 10 NM

S = 5 kts

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D = 6 NM

S = 5 kts

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D = 12 NM

S = 7

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A couple of handy rules to remember:

The 6 minute rule:

Whenever you have traveled for 6 minutes (or as we know 1/10 of an hour)

speed is determined by moving the decimal of the distance one place to the right

For Example:

Travel 2 NM in 6 minutes - speed = 20.0 kts 2/.1 = 20

Travel 2.5 NM for 6 minutes – speed = 25 kts

Travel 1 NM in 6 minutes = speed = 10 kts

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The 3 minute rule:

If you add two zeros to your speed, you will have the distance in yards that you will have traveled in three minutes

For Example:

Your speed is 3 kts – In 3 minutes you will have traveled 300 yards

If your speed is 5 kts – In 3 minutes you will have traveled 500 yards

So . . . now lets put it all together:

You’ve already computed the distances between some of these points:

(See your answers on page 14), or measure again just to make sure . . .

| 1. “2” Buoy south of Point Judith to Green Bell “1B1” north of Block Island |

| |

|Distance = _____________ |

| |

|How long will it take you to travel this distance at 13 kts __________ |

| |

|Assuming the time you took to travel between these two points was 2 hours – what was your speed? ________________ |

| |

| |

|2. Buoy “2” (North of Block Island) to Brenton Reef (Horn) |

| |

|Distance = _______________ |

| |

|How long will it take you to travel this distance at 5 kts? ___________ |

| |

|Assuming it took you 30 minutes – what was your speed? ___________ |

| |

| |

|3. “2” Buoy south of Point Judith to W or “A” Bell |

| |

|Distance: _________________ |

| |

|How long will it take you to travel this distance at 5 kts? ___________ |

| |

|Assuming it took you 30 minutes – what was your speed? ___________ |

| |

| |

|4. Red Buoy “VS (SE of Cuttyhunk) to Green Buoy “29” (E of Gay Head): |

| |

|Distance : _________________ |

| |

|How long will it take you to travel this distance at 12 knots? ___________ |

| |

|Assuming it took you 15 minutes – what was your speed? ____________ |

| |

| |

|5. Green Buoy “29” to Black & White “VS” Whistle: |

| |

|Distance : _________________ |

| |

|How long will it take you to travel this distance at 12 knots? ___________ |

| |

|Assuming it took you 15 minutes – what was your speed? ____________ |

| |

| |

| |

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The formula you are using in your head is:

Minutes

60. = hours

So . . . 30

60 = .5

The formula you are using in your head is:

Minutes

60 = hours

What’s the formula here:

Easy

Hours x 60 = minutes

.2 x 60 = 12

Want it easier????

Forget the decimal;

2 x 60 = 120 – now move the decimal 1 place to the left 120 = 12

Remember to convert hours back to minutes

Multiply by 60

.5 hrs = .5 x 60 = 30 mins

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