Circumference

Warm UpFind the area of each figure.

1. Triangle with base 14 in. and height 10 in.

2. Square with sides of 3.5 feet.

3. Rectangle with length in. and width 6 in.

4. Triangle with base 12.5 m and height 2.4 m.

Complete the table, round to the nearest hundredth.

Object Circumference DiameterBasketball Rim 56.52 in. 18 in.

CD / DVD 37.68 cm 12 cmCoffee Cup 12.56 in. 4 in.Large Pizza 50.24 in. 16 in.

Classroom Clock 43.96 in. 14 in.

What do you notice about the ratio ?

An irrigation sprinkler waters a circular region with a radius of 14 feet. Find the circumference of

the region watered by the sprinkler. Use for π.

Find the circumference of the circle to the nearest hundredth.

When is it logical to use instead of 3.14 for ?

A circular pond has a circumference of 628 feet. A model boat is moving directly

across the pond, along a radius, at a rate of 5 feet per second. How long does it take the boat to get from the edge of the pond to the

center?

• Dante checks the answer to Step 1 by multiplying it by 6 and comparing it with the given circumference. Explain why Dante’s estimation method works.

• Suppose the model boat were traveling at a rate of 4 feet per second. How long would it take the model boat to get from the edge of the pond to the center?

A circular garden has a circumference of 44 yards. Lars is

digging a straight line along a diameter of the garden at a rate of 7 yards per hour. How many hours

will it take him to dig across the garden?