PSLE
Erny and Lily started jogging from the same point of the 12 km track round a housing estate. They started at the same time but in opposite directions. Erny jogged past Lily after 10 km. Both of them did not change their speeds throughout. Erny 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
= 12 - 10
= 2 km

Time that Erny took to jog 12 km = 15 min

Time that Erny took to jog 1 km
= 15 ÷ 12
= 1.25 min

Time that Erny took to jog 10 km
= 10 x 1.25
= 12.5 min

When Erny took 12.5 min to jog 10 km, Lily took the same time to jog 2 km.

1 km = 1000 m
2 km = 2000 m

Lily's jogging speed
= 2000 ÷ 12.5
= 160 m/min

Answer(s): 160 m/min