a car travels certain distance at speed 60km/hour.if it is increases its speed by 15km/hour it travels the same distance in half an hour less.find the distance

Question

how to solve the problem if the answer is 150 km

 

Answer 1

distance = rate*time

 

If he drives t hours at 60 kph, then the time at 75kph

is (t-0.5) hours.  Make 2 equations:

 

d = 60t

d = 75(t - 0.5)

Distance is the same in either case so:

 

75(t-0.5) = 60t

75t - 37.5 = 60t

15t = 37.5

t = 37.5/15

t = 2.5 hours

 

d = 60t = 60(2.5) = 150 km