Anna started jogging from the museum to the garden at a speed of 105 m/min at 7 a.m. Her cousin started jogging from the museum later. They were beside each other at 7.45 a.m. and her cousin reached the garden at 8 a.m. while Anna was still 1800 m away. If both of them travelled at a constant speed throughout the journey, what time did her cousin leave the museum?
1 h = 60 min

From 7 a.m. to 8 a.m. = 1 h
From 7.45 a.m. to 8 a.m. = 15 min

Distance between the museum and the garden
= 60 x 105 + 1800
= 6300 + 1800
= 8100 m

Distance that Anna's cousin had to cover to catch up with Anna
= 45 x 105
= 4725 m

Distance that Anna's cousin travelled to the garden after catching up with Anna
= 8100 - 4725
= 3375 m

Since Anna's cousin jogged 3375 m in 45 min,
Anna's cousin average speed
= 3375 ÷ 15
= 225 m/min

Duration that Anna's cousin took to jog to the garden
= 8100 ÷ 225
= 36 min

Time that Anna's cousin left the museum:
36 min before 8 a.m. = 7.24 a.m.

Answer(s): 7.24 a.m.