Question

A light aircraft travels 6 miles per hour less than three times the speed of a van. If the van can travel 72 miles in the same time it takes the aircraft to travel 204 miles, then what is the average speed of each?

Answer 1

Van: 36 mph.

Plane: 102 mph.

Explanation:

x = speed of van

y = common time value

(3x - 6) * y = 204 // plane

x * y = 72 // van

3xy - 6y = 204 // plane simplified

We can now substitute 72 for xy in the equation above.

3*72 - 6y = 204 --> 216 - 6y = 204

We now subtract 216 from both sides.

-6y = -12

We now divide both sides by -1 to get rid of the negative sign & then divide both sides by 6 to simplify.

y = 2

If x*y = 72, then x = 72/y = 72/2 = 36.

Thus, the speed of the van is 36 mph.

We can find the speed of the plane by using the equation from earlier, 3x - 6.

3x - 6 = 3*36 - 6 = 108 - 6 = 102.