At 14 50, Sam left Town L for Town M, driving at a speed of 70 km/h. At 17 50, Henry also left Town L for Town M driving at a certain speed. Both of them did not change their speed throughout the journey. At 19 50, both of them passed a library that was 280 km away from Town M. How many minutes earlier did Henry reach Town M than Sam?
Duration that Sam travelled from 14 50 to 19 50 = 5 h
Distance that Sam travelled
= 5 x 70
= 350 km
Distance between Town L and Town M
= 350 + 280
= 630 km
Since Henry passed the library at the same time as Sam, it means that Henry travelled 350 km in 2 hours.
Henry's speed during the journey
= 350 ÷ 2
= 175 km/h
Duration that Henry took to reach Town M after passing the library
= 280 ÷ 175
= 1.6 h
Duration that Sam took to reach Town M after passing the library
= 280 ÷ 70
= 4 h
Difference between the time they took to reach Town M
= 4 - 1.6
= 2.4 h
1 h = 60 min
2.4 h = 2.4 x 60 = 144 min
Henry reached Town M 144 minutes earlier than Sam.
Answer(s): 144 min
