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McGraw Hill Integrated II, 2012 View details

1. Circles and Circumference

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Exercise 38 Page 720

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

Diameter: 11.14x cm
Radius: 5.57x cm

Practice makes perfect

Let's find first the radius and then the diameter.

Radius

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 35xcm. By substituting 35x for C in the formula, we can solve for r.

C=2π r

Substitute

C= 35x

35x=2π r

▼

Simplify

CommutativePropMult

Commutative Property of Multiplication

35x=2π (r)

DivEqn

.LHS /2π.=.RHS /2π.

35x/2π=r