PSLE
Mandy and Molly 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 Molly after 10 km. Both of them did not change their speeds throughout. Mandy took 30 min to complete one round. What was Molly's jogging speed in m/min?
Distance that Molly jogged when they passed each other
= 15 - 10
= 5 km

Time that Mandy took to jog 15 km = 30 min

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

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

When Mandy took 20 min to jog 10 km, Molly took the same time to jog 5 km.

1 km = 1000 m
5 km = 5000 m

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

Answer(s): 250 m/min