Kimberly started jogging from the bistro to the park at a speed of 96 m/min at 9 a.m. Her sister started jogging from the bistro later. They were beside each other at 9.35 a.m. and her sister reached the park at 10 a.m. while Kimberly was still 1600 m away. If both of them travelled at a constant speed throughout the journey, what time did her sister leave the bistro?
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 bistro and the park
= 60 x 96 + 1600
= 5760 + 1600
= 7360 m

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

Distance that Kimberly's sister travelled to the park after catching up with Kimberly
= 7360 - 3360
= 4000 m

Since Kimberly's sister jogged 4000 m in 35 min,
Kimberly's sister average speed
= 4000 ÷ 25
= 160 m/min

Duration that Kimberly's sister took to jog to the park
= 7360 ÷ 160
= 46 min

Time that Kimberly's sister left the bistro:
46 min before 10 a.m. = 9.14 a.m.

Answer(s): 9.14 a.m.