Question

A car travels 20 km at a uniform speed of 40 km/h and the next 20 km at a uniform speed of 60 km/h. Find its average speed​

Answer 1

Answer:

Time taken by the car to travel first 20km=20/40=1/2hrs.

Time taken by the car to travel another 20km=20/60=1/3hrs

Total time=1/2+1/3=5/6hrs

Average speed=total distance/total time

=40/5/6=48km/hr

Answer 2

Answer:

48km/h is the  required average speed.

Explanation:

Given in the question, a car travels 20 km at a uniform speed of 40km/h.

And the next 20 km at a uniform speed of 60km/h.

• Average speed - The overall distance the object covers in a given amount of time is its average speed.

• A scalar value represents the average speed. It has no direction and is indicated by the magnitude.

Average speed = $\frac{Total \ distance\ }{Total\ time \ taken}$

Time taken to travel 20km at a uniform speed of 40km/h

Time = $\frac{distance}{speed}$ = $\frac{20}{40}$ = $\frac{1}{2}$h

And, time taken to travels 20 km at a uniform speed of 60km/h

Time = $\frac{distance}{speed}$ = $\frac{20}{60}$ = $\frac{1}{3}$h

Now, average speed = $\frac{Total \ distance\ }{Total\ time \ taken}$

⇒ Average speed = $\frac{20 + 20}{\frac{1}{2} + \frac{1}{3} }$ = $\frac{40}{\frac{5}{6} }$ = $\frac{40 . (6)}{5}$ = 8 × 6 = 48km/h

Hence, the average speed is 48km/h

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