PSLE
Lily and Riley started jogging from the same point of the 15 km track round a nature reserve. They started at the same time but in opposite directions. Lily jogged past Riley after 12 km. Both of them did not change their speeds throughout. Lily took 30 min to complete one round. What was Riley's jogging speed in m/min?
Distance that Riley jogged when they passed each other
= 15 - 12
= 3 km

Time that Lily took to jog 15 km = 30 min

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

Time that Lily took to jog 12 km
= 12 x 2
= 24 min

When Lily took 24 min to jog 12 km, Riley took the same time to jog 3 km.

1 km = 1000 m
3 km = 3000 m

Riley's jogging speed
= 3000 ÷ 24
= 125 m/min

Answer(s): 125 m/min