Question 16

A truck moves at the speed of 90 km/hr after repairing and moves at the speed of 80 km/hr before repairing. It covers x distance in 8 hours after repairing. How much time (in hours) will it take to cover 4x distance before repairing?

Solution

Speed of truck after repairing = 90 km/hr

Distance covered in 8 hours after repairing = $$x$$ km

Using, speed = distance/time

=> $$90=\frac{x}{8}$$

=> $$x=90\times8=720$$ km

Speed of truck before repairing = 80 km/hr

Now, time taken (in hours) to cover $$4x$$ km before repairing = $$\frac{4\times720}{80}=36$$

=> Ans - (C)

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