Diana started jogging from the bakery to the park at a speed of 102 m/min at 6 a.m. Her sister started jogging from the bakery later. They were beside each other at 6.35 a.m. and her sister reached the park at 7 a.m. while Diana was still 1700 m away. If both of them travelled at a constant speed throughout the journey, what time did her sister leave the bakery?
1 h = 60 min

From 6 a.m. to 7 a.m. = 1 h
From 6.35 a.m. to 7 a.m. = 25 min

Distance between the bakery and the park
= 60 x 102 + 1700
= 6120 + 1700
= 7820 m

Distance that Diana's sister had to cover to catch up with Diana
= 35 x 102
= 3570 m

Distance that Diana's sister travelled to the park after catching up with Diana
= 7820 - 3570
= 4250 m

Since Diana's sister jogged 4250 m in 35 min,
Diana's sister average speed
= 4250 ÷ 25
= 170 m/min

Duration that Diana's sister took to jog to the park
= 7820 ÷ 170
= 46 min

Time that Diana's sister left the bakery:
46 min before 7 a.m. = 6.14 a.m.

Answer(s): 6.14 a.m.