PSLE
Mary and Emily started jogging from the same point of the 6 km track round a nature reserve. They started at the same time but in opposite directions. Mary jogged past Emily after 4 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
= 6 - 4
= 2 km

Time that Mary took to jog 6 km = 15 min

Time that Mary took to jog 1 km
= 15 ÷ 6
= 2.5 min

Time that Mary took to jog 4 km
= 4 x 2.5
= 10 min

When Mary took 10 min to jog 4 km, Emily took the same time to jog 2 km.

1 km = 1000 m
2 km = 2000 m

Emily's jogging speed
= 2000 ÷ 10
= 200 m/min

Answer(s): 200 m/min