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49) How much more does he run?

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49) How much more does he run?

by ern5231 » Wed May 12, 2010 1:22 am
Two people run 10 laps around a circular track. The width of the track is 15 feet. One person runs around the outer track and one around the inner. How many additional feet does the person on the inner track run if both are running at the same speed?

I don't have the options to this but this I picked this question from TIME question bank. Any opinions?
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by sanju09 » Wed May 12, 2010 1:37 am
ern5231 wrote:Two people run 10 laps around a circular track. The width of the track is 15 feet. One person runs around the outer track and one around the inner. How many additional feet does the person on the inner track run if both are running at the same speed?

I don't have the options to this but this I picked this question from TIME question bank. Any opinions?
If r feet be the inner track's radius, then r + 15 feet would be the radius of the outer track. One lap around either track is same in length as the circumference of the corresponding circle. The number of additional feet can be found when both have taken 10 laps each, and the difference in the lengths covered by each, is our answer, which is

= 10 × 2 × π × (r + 15 - r)

= [spoiler]300 π feet[/spoiler]
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