Tammy started jogging from the cafe to the reservoir at a speed of 110 m/min at 9 a.m. Her brother started jogging from the cafe later. They were beside each other at 9.32 a.m. and her brother reached the reservoir at 10 a.m. while Tammy was still 1400 m away. If both of them travelled at a constant speed throughout the journey, what time did her brother leave the cafe?
1 h = 60 min

From 9 a.m. to 10 a.m. = 1 h
From 9.32 a.m. to 10 a.m. = 28 min

Distance between the cafe and the reservoir
= 60 x 110 + 1400
= 6600 + 1400
= 8000 m

Distance that Tammy's brother had to cover to catch up with Tammy
= 32 x 110
= 3520 m

Distance that Tammy's brother travelled to the reservoir after catching up with Tammy
= 8000 - 3520
= 4480 m

Since Tammy's brother jogged 4480 m in 32 min,
Tammy's brother average speed
= 4480 ÷ 28
= 160 m/min

Duration that Tammy's brother took to jog to the reservoir
= 8000 ÷ 160
= 50 min

Time that Tammy's brother left the cafe:
50 min before 10 a.m. = 9.10 a.m.

Answer(s): 9.10 a.m.