Question 7

Explanation

This problem is an application of inverse proportion. Since the distance traveled is constant, if the travel time decreases, the speed must increase.

The relationship between speed ($v$) and time ($t$) for a constant distance can be written as:

Given:

• Initial speed $v_1 = 60 \text{ km/h}$
• Initial time $t_1 = 15 \text{ hours}$
• Target time $t_2 = 12 \text{ hours}$

We substitute these values into the equation to find the new speed ($v_2$):

Thus, the speed of the train must be $75 \text{ km/h}$.