Risa started jogging from the temple to the park at a speed of 96 m/min at 6 a.m. Her cousin started jogging from the temple later. They were beside each other at 6.45 a.m. and her cousin reached the park at 7 a.m. while Risa was still 1800 m away. If both of them travelled at a constant speed throughout the journey, what time did her cousin leave the temple?
1 h = 60 min

From 6 a.m. to 7 a.m. = 1 h
From 6.45 a.m. to 7 a.m. = 15 min

Distance between the temple and the park
= 60 x 96 + 1800
= 5760 + 1800
= 7560 m

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

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

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

Duration that Risa's cousin took to jog to the park
= 7560 ÷ 216
= 35 min

Time that Risa's cousin left the temple:
35 min before 7 a.m. = 6.25 a.m.

Answer(s): 6.25 a.m.