Question

The function d(x) = 1375 − 110x represents the distance (in miles) a high-speed

train is from its destination after x hours. (Section 3.3)
a. How far is the train from its destination after 8 hours?
b. How long does the train travel before reaching its destination?

Answer 1

We are given the function:

d (x) = 1375 – 110 x

A. To solve for the distance between the train and its destination after 8 hours, we simply have to plug in, x = 8 into the equation. That is:

d (x) = 1375 – 110 * 8

d (x) = 495 miles

Therefore the train is now only 495 miles away from the destination.

B. To solve for the total time needed to reach its destination, we must set d = 0 and find for the value of x:

0 = 1375 – 110 x

110 x = 1375

x = 12.5 hours

Therefore it takes 12.5 hours for the train to reach its destination.