Date



Reteach

Using Formulas in Geometry

The perimeter of a figure is the sum of the lengths of the sides.

The area is the number of square units enclosed by the figure.

Find the perimeter and area of each figure.

1. rectangle with ( ’ 4 ft, w ’ 1 ft 2. square with s ’ 8 mm

3. 4.

The perimeter of a triangle is the sum of its side lengths.

The base and height are used to find the area.

Perimeter Area

P ’ a + b + c A ’ [pic] bh or [pic]

Find the perimeter and area of each triangle.

5. 6.

Reteach

Using Formulas in Geometry continued

C ’ 2πr A ’ πr 2

C ’ 2π(4) A ’ π(4)2

C ’ 8π A ’ 16π

C < 25.1 m A < 50.3 m2

Find the circumference and area of each circle. Use the ( key on your calculator. Round to the nearest tenth.

7. circle with a radius of 11 inches 8. circle with a diameter of 15 millimeters

9. 10.

11. 12.

Reteach

1. 10 ft; 4 ft2

2. 32 mm; 64 mm2

3. 28 cm; 49 cm2

4. (24 ( 2x) in.; 12x in2

5. (18 ( y) ft; 4y ft2

6. 24.2 cm; 27 cm2

7. 69.1 in.; 380.1 in2

8. 47.1 mm; 176.7 mm2

9. 56.5 in.; 254.5 in2

10. 9.4 cm; 7.1 cm2

11. 81.7 m; 530.9 m2

12. 103.7 mm; 855.3 mm2

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|Figure |Rectangle |Square |

|Model |[pic] |[pic] |

|Perimeter |P ’ 2( + 2w or 2(( + w) |P ’ 4s |

|Area |A ’ (w | A ’ s2 |

|Circles |

| |Circumference |Area |

|Models | | |

|Words |pi times the diameter or 2 times pi times the |pi times the square of the radius |

| |radius | |

|Formulas |C ’ πd or C ’ 2πr |A ’ πr 2 |

space

inside

the circle

distance around

the circle

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