# Help with Circles and Revolutions

• Jan 5th 2013, 03:28 PM
Espionage
Help with Circles and Revolutions
There are 1760 yards in a mile. A certain wheel makes 17,600 revolutions in 40 miles. What is the number of yards in the radius of the wheel? Give your answer as a decimal to the nearest tenth of a mile.
• Jan 5th 2013, 03:38 PM
skeeter
Re: Help with Circles and Revolutions
the wheel travels a distance of $\displaystyle \frac{40 \cdot 1760}{17600} = 4 \, yds$ in one revolution, so that would mean the wheel's circumference is 4 yds, correct?
• Jan 5th 2013, 03:39 PM
Espionage
Re: Help with Circles and Revolutions
Oh, thank you so much!
• Jan 5th 2013, 03:52 PM
HallsofIvy
Re: Help with Circles and Revolutions
So you got the radius from that?
• Jan 6th 2013, 02:14 PM
Espionage
Re: Help with Circles and Revolutions
Well if the circumference is 4 yards, then you can divide it by 2 to get the radius.
• Jan 6th 2013, 02:20 PM
skeeter
Re: Help with Circles and Revolutions
Quote:

Originally Posted by Espionage
Well if the circumference is 4 yards, then you can divide it by $\displaystyle 2\color{red}\pi$ to get the radius.

correction ...