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

Time that Mandy took to jog 15 km = 15 min

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

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

When Mandy took 12 min to jog 12 km, Lily took the same time to jog 3 km.

1 km = 1000 m
3 km = 3000 m

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

Answer(s): 250 m/min