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

Time that Mara took to jog 15 km = 15 min

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

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

When Mara took 12 min to jog 12 km, Molly took the same time to jog 3 km.

1 km = 1000 m
3 km = 3000 m

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

Answer(s): 250 m/min