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McGraw Hill Integrated II, 2012

MH

McGraw Hill Integrated II, 2012 View details

1. Circles and Circumference

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Exercise 25 Page 720

What is the formula for finding the circumference of a circle?

Radius: 19.74ft
Diameter: 39.47ft

Practice makes perfect

Let's find the radius and the diameter of the circle separately. The circumference C of a circle with radius r is calculated using the formula below. C=2π rFrom the exercise, we know that the circumference of the circle is 124ft. By substituting 124 for C in the formula, we can solve for r.

C=2π r

C= 124

124=2π r

.LHS /2.=.RHS /2.

62 = π r

.LHS /π.=.RHS /π.

62/π = r

Rearrange equation

r = 62/π

Use a calculator

r=19.735212 ...

Round to 2 decimal place(s)

r≈ 19.74

The radius of the circle is approximately 19.74ft. Now, to find the diameter, we can multiply the radius by 2. 2* 62/π ≈ 39.47ft

Subchapter links

Exercises p.719-723