Posted by **robert** on Tuesday, November 13, 2007 at 5:02pm.

A ball rolls along a circle whose radius is 2 ft. How far does the ball roll if it goes around the circle 12.5 times?

I got 25 ft as my answer. I just multiplied the two numbers and I got 25. Is this right?

- math -
**bobpursley**, Tuesday, November 13, 2007 at 5:04pm
Nope. The distance around the circle is PI*4.

PI*4*12.5= ? way over 25. Way over 100, but not over 200

- math -
**robert**, Tuesday, November 13, 2007 at 5:07pm
is it 157.1?

- math -
**Ms. Sue**, Tuesday, November 13, 2007 at 5:12pm
I got 157 feet.

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**robert**, Tuesday, November 13, 2007 at 5:15pm
how did you get that?

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**Ms. Sue**, Tuesday, November 13, 2007 at 5:06pm
Oops. I assume the ball is rolling around the circumference of the circle, not the radius.

To find the circumference of the circle, use this formula, in which C = circumference, r = radius, and pi - 3.14

C = 2r * pi

C = 4 * 3.14

C = ?

Now multiply 12.5 by the circumference.

If you post your answer we'll check it. You can also study about the circumference at this site.

http://www.mathgoodies.com/lessons/vol2/circumference.html

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