At 10 40, Mark left Town A for Town B, driving at a speed of 84 km/h. At 12 40, Tim also left Town A for Town B driving at a certain speed. Both of them did not change their speed throughout the journey. At 15 40, both of them passed a clinic that was 252 km away from Town B. How many minutes earlier did Tim reach Town B than Mark?

Distance that Mark travelled
= 5 x 84
= 420 km

Distance between Town A and Town B
= 420 + 252
= 672 km

Since Tim passed the clinic at the same time as Mark, it means that Tim travelled 420 km in 3 hours.

Tim's speed during the journey
= 420 ÷ 3
= 140 km/h

Duration that Tim took to reach Town B after passing the clinic
= 252 ÷ 140
= 1.8 h

Duration that Mark took to reach Town B after passing the clinic
= 252 ÷ 84
= 3 h

Difference between the time they took to reach Town B
= 3 - 1.8
= 1.2 h

1 h = 60 min
1.2 h = 1.2 x 60 = 72 min

Tim reached Town B 72 minutes earlier than Mark.

Answer(s): 72 min