Anna started jogging from the church to the garden at a speed of 110 m/min at 7 a.m. Her sister started jogging from the church later. They were beside each other at 7.32 a.m. and her sister reached the garden at 8 a.m. while Anna was still 1400 m away. If both of them travelled at a constant speed throughout the journey, what time did her sister leave the church?
1 h = 60 min

From 7 a.m. to 8 a.m. = 1 h
From 7.32 a.m. to 8 a.m. = 28 min

Distance between the church and the garden
= 60 x 110 + 1400
= 6600 + 1400
= 8000 m

Distance that Anna's sister had to cover to catch up with Anna
= 32 x 110
= 3520 m

Distance that Anna's sister travelled to the garden after catching up with Anna
= 8000 - 3520
= 4480 m

Since Anna's sister jogged 4480 m in 32 min,
Anna's sister average speed
= 4480 ÷ 28
= 160 m/min

Duration that Anna's sister took to jog to the garden
= 8000 ÷ 160
= 50 min

Time that Anna's sister left the church:
50 min before 8 a.m. = 7.10 a.m.

Answer(s): 7.10 a.m.