Two trains are traveling between city A and city B a distance of 4000 kilometers (km). The regular train travels at a speed of 80 kilometers per hour (km/h). The express train leaves at the same time on a parallel track and travels at 100 km/h. The formula for speed (S) is S=DT where S is speed, D is distance and T is time. How much earlier will the express train arrive at city B? * 10 points

10 hours earlier than regular train

Explanation:

In this case you are already giving the expression to be used which is:

S = D/t   (1)

The problem is giving us the data of the speed of both trains, and we also know the distance between City A and B, which is 4000 km, therefore, we just need to solve for t in the above expression for both trains, and then, do the difference between their times and see how much earlier the express train arrives.

Solving for t, we have:

t = D/S   (2)

For Train 1 (The regular):

t₁ = 4000 / 80

t₁ = 50 h

For Train 2 (Express):

t₂ = 4000 / 100

t₂ = 40 h

Now, as expected express train arrives earlier, now let's see how much:

T = t₁ - t₂

T = 50 - 40

Therefore, Express train arrives 10 hours earlier than regular train.

Hope this helps

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