Jade started jogging from the mall to the nature reserve at a speed of 96 m/min at 9 a.m. Her cousin started jogging from the mall later. They were beside each other at 9.35 a.m. and her cousin reached the nature reserve at 10 a.m. while Jade was still 1800 m away. If both of them travelled at a constant speed throughout the journey, what time did her cousin leave the mall?
1 h = 60 min

From 9 a.m. to 10 a.m. = 1 h
From 9.35 a.m. to 10 a.m. = 25 min

Distance between the mall and the nature reserve
= 60 x 96 + 1800
= 5760 + 1800
= 7560 m

Distance that Jade's cousin had to cover to catch up with Jade
= 35 x 96
= 3360 m

Distance that Jade's cousin travelled to the nature reserve after catching up with Jade
= 7560 - 3360
= 4200 m

Since Jade's cousin jogged 4200 m in 35 min,
Jade's cousin average speed
= 4200 ÷ 25
= 168 m/min

Duration that Jade's cousin took to jog to the nature reserve
= 7560 ÷ 168
= 45 min

Time that Jade's cousin left the mall:
45 min before 10 a.m. = 9.15 a.m.

Answer(s): 9.15 a.m.