Lucy started jogging from the temple to the reservoir at a speed of 105 m/min at 8 a.m. Her sister started jogging from the temple later. They were beside each other at 8.41 a.m. and her sister reached the reservoir at 9 a.m. while Lucy was still 1900 m away. If both of them travelled at a constant speed throughout the journey, what time did her sister leave the temple?
1 h = 60 min

From 8 a.m. to 9 a.m. = 1 h
From 8.41 a.m. to 9 a.m. = 19 min

Distance between the temple and the reservoir
= 60 x 105 + 1900
= 6300 + 1900
= 8200 m

Distance that Lucy's sister had to cover to catch up with Lucy
= 41 x 105
= 4305 m

Distance that Lucy's sister travelled to the reservoir after catching up with Lucy
= 8200 - 4305
= 3895 m

Since Lucy's sister jogged 3895 m in 41 min,
Lucy's sister average speed
= 3895 ÷ 19
= 205 m/min

Duration that Lucy's sister took to jog to the reservoir
= 8200 ÷ 205
= 40 min

Time that Lucy's sister left the temple:
40 min before 9 a.m. = 8.20 a.m.

Answer(s): 8.20 a.m.