Question

A tourist was planning a trip by car for traveling at some constant speed for 2.5 hours. However, he found that if he increases the speed by 20 km/h he can cover the same distance in 30 minutes less time than it was planned. What was the planned speed of the tourist, in km/h?

Answer 1

80 km/h

Explanation:

Let p represent the planned speed in km/h. Using the relation ...

... distance = speed × time

we can take advantage of the fact that the planned trip distance did not change.

... p × 2.5 = (p+20) × (2.5 -0.5)

... 2.5p = 2p +40 . . . . simpify

... 0.5p = 40 . . . . . . . . subtract 2p

... p = 80 . . . . . . . . . . . divide by 0.5

The planned speed was 80 km/h.