Question

Joe runs one lap around a track in 80 seconds. Joe and Jim start at the same point and run the track in opposite directions. They meet in 30 seconds. How long does it take Jim to run the lap?

Answer 1

Joe runs one lap around a track in 80 seconds. Joe and Jim meet after 30 seconds.We know how long does it take for Joe to run one lap, so we can calculate what distance he runs in 30 seconds:
He runs half lap for 40 seconds. He runs quarter lap for 20 minutes and he runs 1/8 lap for ten minutes. So for 30 seconds he runs 3 * 1/8 lap=3/8 lap.
Because Jim runs in opposite direction this means that he will meat with Joe at 1-3/8=5/8 lap. So, Jim runs 5/8 lap for 30 seconds.
1/8 lap Jim runs for 30/5=6 seconds, so Jim needs 8*6=48 seconds to run the lap.
 After 30 seconds Joe has run e runs