Question

Two cars leave a gas station at the same time, one traveling north and the other south. The northbound car travels at 50 mph. After 3 hours the cars are 345 miles apart. How fast is the southbound car traveling?
a.
60 mph
b.
65 mph
c.
70 mph
d.
75 mph

Answer 1

For this case we have:

We define the following variable

x : Speed of the car in South direction

By definition, we know that:

$Distance = Speed * Time$

For the car in north direction:

$D1 = V1 * T1\\D1 = 50mph * 3h\\D1 = 150 miles$

For the car in south direction:

$D2 = V2 * T2\\D2 = x * 3\\D2 = 3x$

The distance between both cars, after 3 hours, is:

$D = D1 + D2$

So, we have:

$345 = 150 + 3x$

Clearing x;

$3x = 345-150\\3x = 195\\x = 65$

Thus, the speed of the car in the south direction is $x = 65mph$

Answer:

Option B