PSLE
Mary and Sonia started jogging from the same point of the 15 km track round a lake. They started at the same time but in opposite directions. Mary jogged past Sonia after 10 km. Both of them did not change their speeds throughout. Mary took 30 min to complete one round. What was Sonia's jogging speed in m/min?
Distance that Sonia jogged when they passed each other
= 15 - 10
= 5 km

Time that Mary took to jog 15 km = 30 min

Time that Mary took to jog 1 km
= 30 ÷ 15
= 2 min

Time that Mary took to jog 10 km
= 10 x 2
= 20 min

When Mary took 20 min to jog 10 km, Sonia took the same time to jog 5 km.

1 km = 1000 m
5 km = 5000 m

Sonia's jogging speed
= 5000 ÷ 20
= 250 m/min

Answer(s): 250 m/min