Many tires come with 13/32 inch of tread. The first 2/32 inch wears off quickly(say during the first 1000miles). From then on the tire wears uniformly. A tire is considerd "worn out" when on 2/32 inch of tread is left.

Question

a. how many 32nds of an inch of usuable tread does a tire have after 1000miles?

b. A tire has traveled 20,000 miles and has 5/32 inch of tread remaining. At this rate how many total miles should the tire last before it is considered worn out?

Answer 1

a. (13-2)/32 =

b. @1000 it had 11/32. @20000 it had 5/32.

So after 19,000 it lost 6/32.

It needs to lose another 3/32 to be "worn out".

You should be able to see the number of miles from that.