Answer
Find out the how far will the model travel in 20 revolutions .
To proof
Formula

where r = radius
As given in the question
A model car has tires that are 2 inches in diameter.

Radius = 1 inches
than

the circumference of the circle = 2 × 3.14
= 6.28 inches
the model travel in 20 revolutions = 20× 6.28
= 125.6 inches
125.6 inches will the model travel in 20 revolutions
Hence proved