Distance fixed; required speed for shorter time A train runs at 96 km/h and covers a trip in 1 h 40 min (100 min). To reduce the journey time to 1 h 20 min (80 min), what average speed is required?

Introduction / Context:
For the same route, the distance remains constant. If you shorten the time, the speed must increase in the ratio distance/time. Compute the original distance and then divide by the new time to get the required speed.

Given Data / Assumptions:

• Original speed = 96 km/h.
• Original time = 100 min = 5/3 h.
• Target time = 80 min = 4/3 h.

Concept / Approach:
Distance D = v * t. Required speed v' = D / t'.

Step-by-Step Solution:

Verification / Alternative check:
At 120 km/h, time = 160 / 120 = 4/3 h = 80 min.

Why Other Options Are Wrong:
90 is slower than before; 144 or 150 overshoot the need.

Common Pitfalls:
Mixing minutes and hours; always convert times to the same unit.

Final Answer:
120 km/h