How long will it take joe to catch up to bob when joe is travellling at 70mph and bob is 80 miles ahead travelling at 50mph?

Question

Bob is 80 miles ahead of joe travelling at 50mph. How long will it take joe to catch up travelling at 70mph?

Answer 1

Work out their relative speed=70-50=20mph.

Time to catch up is 80/20=4 hours.

In this time Bob has travelled 4*50=200 miles and Joe 4*70=280 miles. So Joe has covered the 80 miles between them and a further 200 miles, which means he caught up with Bob.