Question

Bob, driving a new Ford, travels 330 miles in the same amount of time it takes John, driving an old Chevy and traveling 10 miles per hour faster, to travel 390 miles. How fast is Bob driving?

Answer 1

55 mph

Explanation:

Let x represent Bob's speed. Then John's speed is x+10, and their respective times are found by ...

time = distance/speed

330/x = 390/(x+10) . . . . . . . the times are the same

330(x +10) = 390x . . . . . . . multiply by x(x+10)

3300 = 60x . . . . . . . . . . . . . subtract 330x

55 = x . . . . . . . . . . . . . . . . . . divide by the coefficient of x

Bob is driving at 55 miles per hour.