Question

A freight train starts from Los Angeles and heads for Chicago at 40mph. Two hours later a passenger train leaves the same station for Chicago traveling at 60mph. How long will it be before the passenger train overtakes the freight train?

Answer 1

Explanation:

Let's call the time in hours after which the passenger train overtakes the freight train as t.

The distance traveled by the freight train after t hours is 40t.

The distance traveled by the passenger train after t hours is 60(t-2).

At the moment when the passenger train overtakes the freight train, their distances must be equal:

40t = 60(t-2)

Expanding the second term, we get:

40t = 60t - 120

Subtracting 40t from both sides, we get:

0 = 20t - 120

Adding 120 to both sides, we get:

120 = 20t

Dividing both sides by 20, we get:

t = 6

So it will take 6 hours for the passenger train to overtake the freight train.