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

Time that Mary took to jog 15 km = 15 min

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

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

When Mary took 12 min to jog 12 km, Emily took the same time to jog 3 km.

1 km = 1000 m
3 km = 3000 m

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

Answer(s): 250 m/min