Question

Speed. One car travels 12 mph faster than another. While one car

travels 141 mi, the other travels 105 mi. How fast is each car
traveling?

Answer 1

Answer: the speeds of the cars are 47mph for the faster one, and 35mph for the slower one.

Explanation:

Here you must remember the relation:

Speed = distance/time.

So we have car A and car B, with Sa the speed of car A, and Sb the speed of car B.

We know that:

Sa = Sb + 12mph.

and in the same time T, car A travels 141mi, while car B travels 105mi, then we have:

Sa*T = 141mi

Sb*t = 105mi

we can take the quotient of those two and get:

(Sa/Sb) = 141/105.

now we can replace Sa by Sa = Sb + 12mph.

(Sb + 12mph)/(Sb) = 141/105.

Sb + 12mph = (141/105)*Sb

Sb*(141/105 - 1) = 12mph

Sb = 12mph/(141/105 - 1) = 35mph.

and we know that:

Sa = Sb + 12mph = 35mph + 12mph = 47mph.