Xylia started jogging from the cinema to the nature reserve at a speed of 114 m/min at 8 a.m. Her sister started jogging from the cinema later. They were beside each other at 8.35 a.m. and her sister reached the nature reserve at 9 a.m. while Xylia was still 1900 m away. If both of them travelled at a constant speed throughout the journey, what time did her sister leave the cinema?
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 cinema and the nature reserve
= 60 x 114 + 1900
= 6840 + 1900
= 8740 m

Distance that Xylia's sister had to cover to catch up with Xylia
= 35 x 114
= 3990 m

Distance that Xylia's sister travelled to the nature reserve after catching up with Xylia
= 8740 - 3990
= 4750 m

Since Xylia's sister jogged 4750 m in 35 min,
Xylia's sister average speed
= 4750 ÷ 25
= 190 m/min

Duration that Xylia's sister took to jog to the nature reserve
= 8740 ÷ 190
= 46 min

Time that Xylia's sister left the cinema:
46 min before 9 a.m. = 8.14 a.m.

Answer(s): 8.14 a.m.