1.

A car travels at a speed of 50km/h for 30min , at 30km/h for the next 15min and thenat 70km/h for next 45min what is the average speed of car?​

Answer»

Answer:-

Given:-

SPEED of the car in first 30 MIN = 50 km/h.

We know that,

Distance = Speed × time.

So,

⟹ Distance travelled by car in first 30 min = 50 × (30/60)

[ ∵ 1 MINUTE = 1/60 hrs ]

⟹ Distance travelled by car in first 30 min = 25 km

Also given that,

Speed of the car for NEXT 15 min = 30 km/hr

So, Distance travelled by the car for next 15 min = 30 × (15/60)

⟹ Distance travelled by the car for next 15 min = 7.5 km

Speed of the car in last 45 min = 70 km/h

⟹ Distance travelled by car in last 45 min = 70 × (45/60)

⟹ Distance travelled by car in last 45 min = 52.5 km

We know that,

Average speed = Total distance travelled/total time taken.

We have:-

  • Total distance = (25 + 7.5 + 52.5) km = 85 km.

  • Total time = 30 + 15 + 45 = 90 min = 90/60 hrs = 3/2 hrs.

So,

⟹ Average speed of the car = 85 / (3/2)

⟹ Average speed of the car = 85 × (2/3)

⟹ Average speed of the car = 56.66 km/hr

∴ The Average speed of the car is 56.66 km/hr.


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