At 10 20, Ahmad left Town C for Town D, driving at a speed of 93 km/h. At 11 20, Billy also left Town C for Town D driving at a certain speed. Both of them did not change their speed throughout the journey. At 14 20, both of them passed a school that was 186 km away from Town D. How many minutes earlier did Billy reach Town D than Ahmad?

Distance that Ahmad travelled
= 4 x 93
= 372 km

Distance between Town C and Town D
= 372 + 186
= 558 km

Since Billy passed the school at the same time as Ahmad, it means that Billy travelled 372 km in 3 hours.

Billy's speed during the journey
= 372 ÷ 3
= 124 km/h

Duration that Billy took to reach Town D after passing the school
= 186 ÷ 124
= 1.5 h

Duration that Ahmad took to reach Town D after passing the school
= 186 ÷ 93
= 2 h

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

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

Billy reached Town D 30 minutes earlier than Ahmad.

Answer(s): 30 min