Cathy started jogging from the florist to the park at a speed of 105 m/min at 9 a.m. Her cousin started jogging from the florist later. They were beside each other at 9.45 a.m. and her cousin reached the park at 10 a.m. while Cathy was still 1800 m away. If both of them travelled at a constant speed throughout the journey, what time did her cousin leave the florist?
1 h = 60 min

From 9 a.m. to 10 a.m. = 1 h
From 9.45 a.m. to 10 a.m. = 15 min

Distance between the florist and the park
= 60 x 105 + 1800
= 6300 + 1800
= 8100 m

Distance that Cathy's cousin had to cover to catch up with Cathy
= 45 x 105
= 4725 m

Distance that Cathy's cousin travelled to the park after catching up with Cathy
= 8100 - 4725
= 3375 m

Since Cathy's cousin jogged 3375 m in 45 min,
Cathy's cousin average speed
= 3375 ÷ 15
= 225 m/min

Duration that Cathy's cousin took to jog to the park
= 8100 ÷ 225
= 36 min

Time that Cathy's cousin left the florist:
36 min before 10 a.m. = 9.24 a.m.

Answer(s): 9.24 a.m.