McGraw Hill Integrated II, 2012
MH
McGraw Hill Integrated II, 2012 View details
1. Circles and Circumference
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Exercise 35 Page 720

Practice makes perfect
a We are given that Mr. Martinez is going to build the patio and we want to find the approximate circumference of this patio. Let's take a look at the given diagram.

Now we will recall that the circumference of a circle is two times the product of the radius of a circle and pi. In our exercise the radius of the patio is 3+ 2=5 feet. C=2*5*π≈ 31.42 The circumference of the patio is approximately 31.42 feet.

b In this part we are given that Mr. Martinez changes the plans so that the inner circle has a circumference of approximately 25 feet. To find the radius of the inner circle we will again use the circumference formula.
C=2π r Let's substitute 25 for C and solve for r.
C=2π r
25=2π r
25/2π=r
r=25/2π
r=3.9788...
r≈ 4
The radius of the inner circle should be approximately 4 feet.