Nora started jogging from the school to the reservoir at a speed of 96 m/min at 8 a.m. Her cousin started jogging from the school later. They were beside each other at 8.45 a.m. and her cousin reached the reservoir at 9 a.m. while Nora was still 1800 m away. If both of them travelled at a constant speed throughout the journey, what time did her cousin leave the school?
1 h = 60 min

From 8 a.m. to 9 a.m. = 1 h
From 8.45 a.m. to 9 a.m. = 15 min

Distance between the school and the reservoir
= 60 x 96 + 1800
= 5760 + 1800
= 7560 m

Distance that Nora's cousin had to cover to catch up with Nora
= 45 x 96
= 4320 m

Distance that Nora's cousin travelled to the reservoir after catching up with Nora
= 7560 - 4320
= 3240 m

Since Nora's cousin jogged 3240 m in 45 min,
Nora's cousin average speed
= 3240 ÷ 15
= 216 m/min

Duration that Nora's cousin took to jog to the reservoir
= 7560 ÷ 216
= 35 min

Time that Nora's cousin left the school:
35 min before 9 a.m. = 8.25 a.m.

Answer(s): 8.25 a.m.