Clue 2

Steve's time to jog halfway round = 

Mark's time to jog halfway round = 

Paul's time to jog halfway round = 

The shortest time elapsing before all three boys are on the straight line again at the same time is the smallest number which contains all the fractions 1/35, 1/32 and 3/80 as factors.

That is, find the least common multiple of the three fractions. (A calculator might help!)