PSLE
Opal and Elsa started jogging from the same point of the 15 km track round a housing estate. They started at the same time but in opposite directions. Opal jogged past Elsa after 10 km. Both of them did not change their speeds throughout. Opal took 30 min to complete one round. What was Elsa's jogging speed in m/min?
Distance that Elsa jogged when they passed each other
= 15 - 10
= 5 km

Time that Opal took to jog 15 km = 30 min

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

Time that Opal took to jog 10 km
= 10 x 2
= 20 min

When Opal took 20 min to jog 10 km, Elsa took the same time to jog 5 km.

1 km = 1000 m
5 km = 5000 m

Elsa's jogging speed
= 5000 ÷ 20
= 250 m/min

Answer(s): 250 m/min