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

Time that Emma took to jog 15 km = 15 min

Time that Emma took to jog 1 km
= 15 ÷ 15
= 1 min

Time that Emma took to jog 12 km
= 12 x 1
= 12 min

When Emma took 12 min to jog 12 km, Ruby took the same time to jog 3 km.

1 km = 1000 m
3 km = 3000 m

Ruby's jogging speed
= 3000 ÷ 12
= 250 m/min

Answer(s): 250 m/min