Question

a car travels at a speed of 50kmph for 30 min, at 30kmph for the next 15 min and then at 70kmph for the next 45 min. what is the average speed of the car

Answer 1

Answer:-

56.67km/h

Explanation:-

Let the speeds of the car be v₁ , v₂ and v₃ respectively and the times be t₁ , t₂ and t₃ respectively.

Also let the distances be d₁ , d₂ and d₃ respectively.

Firstly, let's convert the times from

'minute' to 'hour'.

• 1h = 60min

=> t₁ = 30/60 = 0.5h

=> t₂ = 15/60 = 0.25h

=> t₃ = 45/60 = 0.75h

Now,

Distance = Speed × Time

=> d₁ = v₁t₁ = 50(0.5) = 25km

=> d₂ = v₂t₂ = 30(0.25) = 7.5km

=> d₃ = v₃t₃ = 70(0.25) = 52.5km

We know that :-

Avg speed :-

= Total distance / Total time

=> Vₐᵥ = d₁ + d₂ + d₃ / t₁ + t₂ + t₃

=> Vₐᵥ = v₁t₁ + v₂t₂ + v₃t₃ / t₁ + t₂ + t₃

=> Vₐᵥ = [25 + 7.5 + 52.5] / [0.5+0.25+0.75]

=> Vₐᵥ = 85/1.5

=> Vₐᵥ = 56.67km/h

Thus, average speed of the car is 56.67km/h.