A car travels a certain distance with 42km h-1 for 20 minutes and the remaining distance at 60 km h-1 for 30 minutes . what is its average speed of the whole journey?
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Given:-
- Speed of car in 1st case ( s) = 42km/h
- Time taken by car in 1st case (t) =20min = 20/60 = 1/3h.
- Speed of car in 2nd case (s') = 60km/h
- Time taken by car in 2nd case (t') = 1h and 30min = 30/60 = 1/2h
To Find:-
- Average speed of car.
Solution:-
As we know that Average speed is the sum of total distance divided by total time taken.
Firstly we calculate the distance covered by car in both case
For 1st case
→ Distance = speed/time
Substitute the value, we get
→ Distance (d) = 42/1/3 = 14km
And , Now Distance for second Case
→ Distance (d') = speed / time
→ Distance = 60/1/2 = 30km
→ Average Speed = Total Distance/Total Time taken
→ Av. Speed = d+d'/t+t'
→ Av.Speed = 14+30/1/2+1/3
→ Av.Speed = 44/5/6
→ Av.Speed = 36.66km/h
∴ The Av.Speed of the car in whole journey is 36.66km/h.
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