Question

Two cars pass each other on a freeway at 6:30 a.m. The car driving north is

traveling at an average speed of 60 mph and the car driving south is traveling at an
average speed of 40 mph. At what time will they be 25 miles apart?

Answer 1

`\large \boxed{\text{15 min}}`

Explanation:

The cars are diverging at a combined speed of 60 + 40 =100 mi/h.

That is the same as if one car stood still and the other sped away at 100 mi/h.

`\text{Time} = \text{25 mi} * \frac{\text{1 h}}{\text{100 mi}} = \text{0.25 h} = \text{15 min}\\\text{The cars will be 25 mi apart in $\large \boxed{\textbf{15 min}}$}`