Two cars, 136 miles apart, start moving towards each other at the same time. One car is moving in the + x-direction and the other car is moving in the - x-direction. One is moving 3 times as fast as the other. If they meet 1.6 hours later, find the average speed of the slower car in miles per hour.

21.25 miles/hour

Step-by-step explanation:

Let's call the speed of the fast car X, and the speed of the slow car Y.

As they are moving in opposite direction, their relative speed (V) will be the sum of their speeds:

V = X + Y

The fast car is 3 times faster than the slow car, so:

X = 3*Y

They are 136 miles apart, and they meet in 1.6 hours, so we can calculate V:

V * 1.6 = 136

V = 85 miles/hour

using X = 3*Y in the first equation, we have that:

V = 3*Y + Y

85 = 4*Y

Y = 21.25 miles/hour

So the speed of the slower car is 21.25 miles per hour