PSLE
Mary and Anna 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. Mary jogged past Anna after 12 km. Both of them did not change their speeds throughout. Mary took 30 min to complete one round. What was Anna's jogging speed in m/min?
Distance that Anna jogged when they passed each other
= 15 - 12
= 3 km

Time that Mary took to jog 15 km = 30 min

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

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

When Mary took 24 min to jog 12 km, Anna took the same time to jog 3 km.

1 km = 1000 m
3 km = 3000 m

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

Answer(s): 125 m/min