7th Grade Math

556 Volume and Surface Area

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Find the area of each triangle.

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   2. 
      
   
   
   
   


2. YARD Anita’s yard is in the shape of
   a triangle. It has a height of 35 feet
   and a base of 50 feet. What is the area
   of the yard?

EXAMPLE 1

Find the area of the triangle.

12 in.

5 in. 13 in.

A = _^12 bh Area of a triangle

A = _^12 (12)(5) Replace b with 12 and h with 5.

A = _^12 (60) Multiply.

A = 30 Multiply.

The area of the triangle is 30 square inches.

Find the area of each circle. Use 3.14 for

π. Round to the nearest tenth.

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   5. 
      
   
   
   
   


5. PIZZA Find the area of a circular
   pizza with a radius of 6 inches.


6. CUPS A manufacturer measures a
   cup’s diameter to determine how
   much material is needed for a lid.
   The diameter is 10 centimeters. Find
   the area of the lid.

EXAMPLE 2

Find the area of the circle. Use 3.14 for

π. Round to the nearest tenth.

3 cm

Estimate 3.14 × (3)^2 = 3 × 9 or 27

A = πr^2 Area of a circle

A ≈ 3.14 × (3)^2 Replace π with 3.14 and r with 3.

A ≈ 3.14 × 9 Evaluate (3)^2.

A ≈ 28.26 Multiply.

Round to the nearest tenth. The area is

about 28.3 square centimeters.

Check 28.3 ≈ 27 

5 yd

14 yd 10 yd

17 mm

9 mm

24 mm 11 in.

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