Winnie started jogging from the boutique to the nature reserve at a speed of 110 m/min at 5 a.m. Her brother started jogging from the boutique later. They were beside each other at 5.42 a.m. and her brother reached the nature reserve at 6 a.m. while Winnie was still 1800 m away. If both of them travelled at a constant speed throughout the journey, what time did her brother leave the boutique?
1 h = 60 min

From 5 a.m. to 6 a.m. = 1 h
From 5.42 a.m. to 6 a.m. = 18 min

Distance between the boutique and the nature reserve
= 60 x 110 + 1800
= 6600 + 1800
= 8400 m

Distance that Winnie's brother had to cover to catch up with Winnie
= 42 x 110
= 4620 m

Distance that Winnie's brother travelled to the nature reserve after catching up with Winnie
= 8400 - 4620
= 3780 m

Since Winnie's brother jogged 3780 m in 42 min,
Winnie's brother average speed
= 3780 ÷ 18
= 210 m/min

Duration that Winnie's brother took to jog to the nature reserve
= 8400 ÷ 210
= 40 min

Time that Winnie's brother left the boutique:
40 min before 6 a.m. = 5.20 a.m.

Answer(s): 5.20 a.m.