Question

Ron recently increased the size of his Jeep tires from the original P220/75R16 to the larger P250/85R17. If Ron didn'trecalibrate his speedometer, how fast is he really going on the new tires when his speedometer shows he is traveling 60mph?

Answer 1

We can use a ratio to solve this problem

P220/75R16 has a radius of 16

P250/85R17 has a radius of 17

The ratio of the radius of the tire to the speed is a constant

16 17

----- = ----------

60 x

where x is the speed on the speedometer

Using cross products

16x = 60*17

16x = 1020

x = 1020/16

63.75

63.75 mph

The larger the tire, the faster you will be going.