At 11 10, Henry left Town N for Town P, driving at a speed of 84 km/h. At 12 10, Harry also left Town N for Town P driving at a certain speed. Both of them did not change their speed throughout the journey. At 15 10, both of them passed a mall that was 168 km away from Town P. How many minutes earlier did Harry reach Town P than Henry?

Distance that Henry travelled
= 4 x 84
= 336 km

Distance between Town N and Town P
= 336 + 168
= 504 km

Since Harry passed the mall at the same time as Henry, it means that Harry travelled 336 km in 3 hours.

Harry's speed during the journey
= 336 ÷ 3
= 112 km/h

Duration that Harry took to reach Town P after passing the mall
= 168 ÷ 112
= 1.5 h

Duration that Henry took to reach Town P after passing the mall
= 168 ÷ 84
= 2 h

Difference between the time they took to reach Town P
= 2 - 1.5
= 0.5 h

1 h = 60 min
0.5 h = 0.5 x 60 = 30 min

Harry reached Town P 30 minutes earlier than Henry.

Answer(s): 30 min