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

Answer: B. 65 MPH

Explanation:

Answer 2

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