Question

A car covers its journey at the speed of 80 km/hour in 10 hours. If the same distance is
to be covered in 4 hours, by how much the speed of car will have to increase?
(a) 8 km/hr
(b) 10 km/hr
(c) 12 km/hr
(d) 16 km/hr
(e) None of these

Answer 1

initially speed of car = travelled distance/time
=80/10=8kmph


now to cover same distance the new speed of car must be =80/4=20kmph

speed of car will have to increase=20-10
=10kmph

Answer 2

e)because 80 km the car covers in 1 hour
so,we can write
in 1 hour the car covers 80 km
in 10 " " " " " " " =80×10=800km
here the qustion said that the distance is same=800km
in 4 hour the car covers =800km
in 1 " " " " " =800/4 km
=200 km
hence,the speed is now=200 km/h
n the fast speed was = 80 km/h
so the increase speed of the car is=(200-80)km=120km