Question

The distance between two places is 120 km. A car travelling at a certain speed can cover the distance in 2 hours 30 minutes. By how many km/h should the speed of the car be increased for it to take 30 minutes less to cover the distance?

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Answer 1

Distance between two places=120 km

Explanation:

Time= 2 hrs 30 min

=(2*60)min+30min

=120min+30min

=150min=150/60 hr

= 5/2 hr

Speed = distance /time

= (120/5/2)km/hr

=(120×2/5)km/hr

=(240/5)km/hr

= 48 km/hr

New time = 2 hr 30min-30min

= 2hr

Distance =120km

Speed = Distance /time

=120/2 km/hr

= 60 km/hr

Increase in speed=(60-48)km/hr

=12km/hr

Another way to show :

Distance = 120km

speed=Distance/time

=120/2.5=48 km/hr

New speed=120/2=60 Km/hr

change inspeed=60-48=12km/hr