PSLE
Gem and Erny started jogging from the same point of the 15 km track round a lake. They started at the same time but in opposite directions. Gem jogged past Erny after 12 km. Both of them did not change their speeds throughout. Gem took 15 min to complete one round. What was Erny's jogging speed in m/min?
Distance that Erny jogged when they passed each other
= 15 - 12
= 3 km

Time that Gem took to jog 15 km = 15 min

Time that Gem took to jog 1 km
= 15 ÷ 15
= 1 min

Time that Gem took to jog 12 km
= 12 x 1
= 12 min

When Gem took 12 min to jog 12 km, Erny took the same time to jog 3 km.

1 km = 1000 m
3 km = 3000 m

Erny's jogging speed
= 3000 ÷ 12
= 250 m/min

Answer(s): 250 m/min