Posted by **Gabi** on Wednesday, May 11, 2011 at 12:30am.

The speedometer of John's truck uses the revolutions of his tires to calculate the speed of the truck.

How many revolutions per minute do the tires make when the truck is traveling at 55 miles per hour?

(picture with tires with diameter of 26 in.)

Suppose John buys tires with a diametr of 30 inches. When the speedometer reads 55 miles per hour, the tires would still revolve at the same rate as before. However, with the new tires, the truck travels a different distance in each revolution. Calculate the actual speed when the speedometer reads 55 miles per hour.

Thank you so much.

- Math -
**PsyDAG**, Wednesday, May 11, 2011 at 12:58pm
Circumference = π diameter = 3.14 * 26

55 mph = 4,840 feet/hr = 4,840 * 12 inches/hour = 4,840*12inches/60 minutes

Divide the above answer by circumference to get revolutions/minute

Use the above process to get the answer to your second question.

- Math -
**Anonymous**, Monday, April 27, 2015 at 8:05pm
711.4

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