Olivia started jogging from the cinema to the nature reserve at a speed of 110 m/min at 7 a.m. Her brother started jogging from the cinema later. They were beside each other at 7.32 a.m. and her brother reached the nature reserve at 8 a.m. while Olivia was still 1400 m away. If both of them travelled at a constant speed throughout the journey, what time did her brother leave the cinema?
1 h = 60 min

From 7 a.m. to 8 a.m. = 1 h
From 7.32 a.m. to 8 a.m. = 28 min

Distance between the cinema and the nature reserve
= 60 x 110 + 1400
= 6600 + 1400
= 8000 m

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

Distance that Olivia's brother travelled to the nature reserve after catching up with Olivia
= 8000 - 3520
= 4480 m

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

Duration that Olivia's brother took to jog to the nature reserve
= 8000 ÷ 160
= 50 min

Time that Olivia's brother left the cinema:
50 min before 8 a.m. = 7.10 a.m.

Answer(s): 7.10 a.m.