Percent of Change NOTES - Paulding County School District

Name: _________________________

Percent of Change ? NOTES

A change in a quantity is often described as a percent increase or percent decrease. To calculate a percent increase or decrease, use this equation.

percentage of change =

?

Find the percent of change from 28 to 42. ? First, find the amount of the change. 42 28 14

? What is the original amount? 28

? Use the equation.

? = 50%

An increase from 28 to 42 represents a 50% increase.

Find each percent of change.

1. 8 is increased to 22 amount of change 22 8 14 original amount = 8

= 175%

2. 90 is decreased to 81 amount of change 90 81 9 original amount = 90

? = 10%

Simple Interest - Notes

When you put money into a bank account, you may receive simple interest for loaning the bank your money.

Interest Principal ? Rate ? Time I p ? r ? t

You can use the expression

to solve interest problems.

? To find interest (I), put your finger over I. Perform the operations for letters you see.

I = p ? r ? t

? To find principal (p), put your finger over p. Perform the operations for letters you see.

P =

? To find interest rate (r), put your finger over r. Perform the operations for letters you see.

r =

Find each missing value. 1. p $400, r 5%, t 3 years

I p ? r ? t

I 400 ? .05_ ? 3

I $60

3. I $350, r 7%, t 2 years p l r t p p $2,500

2. p $15,000, r 6%, t 2 years I p ? r ? t

I 15,000 ? .06 ? 2

I $1800

4. I $168, p $1,400, t 4 years r l pt r r 3%

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