# Math Help - help

1. ## help

Please help.

A car is traveling at 27mph. if its tires have a diameter of 28in how fast are the cars tires turning? express the answer in revolutions per minute.

2. Originally Posted by donnyB
Please help.

A car is traveling at 27mph. if its tires have a diameter of 28in how fast are the cars tires turning? express the answer in revolutions per minute.
1)
Find how far the car travelled in a minute, then divide by circumference of the tyre.

2)
$v=r\omega$
$\omega =2\pi f$
$f=$?

3. Another way to do that: find the circumference of the tire and divide into 27 miles. One rotation of the tire will cover a distance equal to the circumference of the tire. That will give the number of rotations per hour so multiply by 60 min/hour.