Question

A car travels a certain distance with a speed of 50 krb, and returns with a speed
40 kmh. Calculate the average speed for the whole journey​

Answer 1

Question:

A car travels a certain distance with a speed of 50 km/hr, and returns with a speed 40 km/h. Calculate the average speed for the whole journey.

Solution:

• Let distance covered by car = x

• Total distance covered by car = 2x

(because later the car returns to it's position. So, total distance is distance of going and again returning)

• $S_{1}$ = 50 km/hr

• $S_{2}$ = 40 km/hr

Now ..

Time = $\dfrac{distance}{speed}$

• $t_{1}$ = $\dfrac{x}{50}$

• $t_{2}$ = $\dfrac{x}{40}$

Now

Average Speed = $\dfrac{Total\: distance\:covered}{Toatal\:time\:taken}$

=> $\dfrac{2x}{ \frac{x}{50} \: + \: \frac{x}{40} }$

=> $\dfrac{2x}{ \frac{40x\:+\:50x}{200} }$

=> $\dfrac{2x}{ \frac{90x}{200} }$

=> $\dfrac{400}{9}$

=> 44.44 km/hr

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44.4 km/hr is the average speed of the whole trip.

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