PSLE
Elsa and Gem started jogging from the same point of the 12 km track round a nature reserve. They started at the same time but in opposite directions. Elsa jogged past Gem after 10 km. Both of them did not change their speeds throughout. Elsa took 15 min to complete one round. What was Gem's jogging speed in m/min?
Distance that Gem jogged when they passed each other
= 12 - 10
= 2 km

Time that Elsa took to jog 12 km = 15 min

Time that Elsa took to jog 1 km
= 15 ÷ 12
= 1.25 min

Time that Elsa took to jog 10 km
= 10 x 1.25
= 12.5 min

When Elsa took 12.5 min to jog 10 km, Gem took the same time to jog 2 km.

1 km = 1000 m
2 km = 2000 m

Gem's jogging speed
= 2000 ÷ 12.5
= 160 m/min

Answer(s): 160 m/min