Emma started jogging from the church to the park at a speed of 100 m/min at 5 a.m. Her cousin started jogging from the church later. They were beside each other at 5.36 a.m. and her cousin reached the park at 6 a.m. while Emma was still 1200 m away. If both of them travelled at a constant speed throughout the journey, what time did her cousin leave the church?
1 h = 60 min

From 5 a.m. to 6 a.m. = 1 h
From 5.36 a.m. to 6 a.m. = 24 min

Distance between the church and the park
= 60 x 100 + 1200
= 6000 + 1200
= 7200 m

Distance that Emma's cousin had to cover to catch up with Emma
= 36 x 100
= 3600 m

Distance that Emma's cousin travelled to the park after catching up with Emma
= 7200 - 3600
= 3600 m

Since Emma's cousin jogged 3600 m in 36 min,
Emma's cousin average speed
= 3600 ÷ 24
= 150 m/min

Duration that Emma's cousin took to jog to the park
= 7200 ÷ 150
= 48 min

Time that Emma's cousin left the church:
48 min before 6 a.m. = 5.12 a.m.

Answer(s): 5.12 a.m.