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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Step by step explanation is needed..​

Answer 1

Answer:

Distance between two places=120 km

Step-by-step 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

Answer 2

Distance = 120 km

Time = 2hr 30min

speed = distance/ time

Average speed = 120/ 2.5 because 2h r30min = 2.5 hrs

120/2.5 = 48km/h

2hr30min - 30min = 2hrs

120/2 = 60km/h

=> (60–48)km/h = 12km/h

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