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5. A car moves with a speed of 30 km/h for half an hour, 25 km/h for one hour and 40 km/h for twohours. Calculate the average speed of the car. |
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Answer» Explanation:Solution,Speed = 30 km/hTime taken = 1/2 hourWe know that,DISTANCE = Speed × TimeDistance = 30 × 1/2Distance, D₁ = 15 kmNow, Speed = 25 km/hTime taken = 1 hourDistance = 25 × 1Distance, D₂ = 25 kmSpeed = 40 km/hDistance = 40 × 2Distance, D₃ = 80 kmTotal distance covered = D₁ + D₂ + D₃ = 15 + 25 + 80 = 120 km.Total time taken = 1/2 + 1 + 2 = 3 hr 30 MIN = 7/2 hrsNow, we know that,Average speed = Total distance/Total time taken⇒ Average speed = 120/7/2⇒ Average speed = 120 × 2/7⇒ Average speed = 34.28 km/hHence, the average speed of the car is 34.28 km/h. |
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