Victoria started jogging from the library to the garden at a speed of 115 m/min at 8 a.m. Her cousin started jogging from the library later. They were beside each other at 8.35 a.m. and her cousin reached the garden at 9 a.m. while Victoria was still 1500 m away. If both of them travelled at a constant speed throughout the journey, what time did her cousin leave the library?
1 h = 60 min

From 8 a.m. to 9 a.m. = 1 h
From 8.35 a.m. to 9 a.m. = 25 min

Distance between the library and the garden
= 60 x 115 + 1500
= 6900 + 1500
= 8400 m

Distance that Victoria's cousin had to cover to catch up with Victoria
= 35 x 115
= 4025 m

Distance that Victoria's cousin travelled to the garden after catching up with Victoria
= 8400 - 4025
= 4375 m

Since Victoria's cousin jogged 4375 m in 35 min,
Victoria's cousin average speed
= 4375 ÷ 25
= 175 m/min

Duration that Victoria's cousin took to jog to the garden
= 8400 ÷ 175
= 48 min

Time that Victoria's cousin left the library:
48 min before 9 a.m. = 8.12 a.m.

Answer(s): 8.12 a.m.