A car travels the first 15 km at a uniform speed of 50 kilometre per hour and the last 10 kilometre at a uniform speed of 20 km/h. Calculate the average speed for the entire journey.
Answers
Given :
Given that, a car travels the first 15km at a uniform speed of 50km/hr and the last 10km at a uniform speed of 20km/hr.
To find :
Here, we have to find the average speed of the entire journey of the car.
Explaination :
Here, we are given a car that is traveling the first 15km with a different uniform speed and the last 10km with a different uniform speed. Now, we have to find the average speed for the entire journey. For this, we'll add the distances, time and substitute the values in the formula and solve. Also, here the unit time is an unknown value. So we'll even find the time by Speed = Distance/Time formula.
Solution :
- At first, the car travels 15km at a uniform speed of 50km/hr, so :
»» Speed = Distance/Time
»» Time = Distance/Speed
»» Time¹ = 15/50
»» Time¹ = 3/10hr
- Next, the car travels 10km at a uniform speed of 20km/hr, so :
»» Time = Distance/Speed
»» Time² = 10/20
»» Time² = 1/2hr
- Total distance covered :
»» Sum of the distances travelled
»» 15km + 10km
»» Total distance = 25km
- Total time taken (T¹ + T²) :
»» Total time = 3/10 + 1/2
»» Total time = 8/10
»» Total time = 4/5hr
- Finding average speed :
»» Average speed = Total distance/T¹ + T²
»» Average speed = 25km/(4/5hr)
»» Average speed = 25(5)/4
»» Average speed = 125/4 km/hr
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Therefore, 125/4 km/hr is the average speed for the entire journey of the car.