PSLE
Riley and Sonia 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. Riley jogged past Sonia after 10 km. Both of them did not change their speeds throughout. Riley took 15 min to complete one round. What was Sonia's jogging speed in m/min?
Distance that Sonia jogged when they passed each other
= 12 - 10
= 2 km

Time that Riley took to jog 12 km = 15 min

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

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

When Riley took 12.5 min to jog 10 km, Sonia took the same time to jog 2 km.

1 km = 1000 m
2 km = 2000 m

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

Answer(s): 160 m/min