PSLE
Penny and Riley started jogging from the same point of the 6 km track round a lake. They started at the same time but in opposite directions. Penny jogged past Riley after 4 km. Both of them did not change their speeds throughout. Penny took 15 min to complete one round. What was Riley's jogging speed in m/min?
Distance that Riley jogged when they passed each other
= 6 - 4
= 2 km

Time that Penny took to jog 6 km = 15 min

Time that Penny took to jog 1 km
= 15 ÷ 6
= 2.5 min

Time that Penny took to jog 4 km
= 4 x 2.5
= 10 min

When Penny took 10 min to jog 4 km, Riley took the same time to jog 2 km.

1 km = 1000 m
2 km = 2000 m

Riley's jogging speed
= 2000 ÷ 10
= 200 m/min

Answer(s): 200 m/min