A train covers 400 km at a uniform speed. If the speed had been 10 km/h more, it would have taken 2 hours less for the same journey. What is the usual time taken (in hours) by it to complete the journey?
Answer & explanation
Correct answer: option 4
Let Usual Speed = S km
According to question ,
\(\frac{400}{S}\) - \(\frac{400}{S + 10 }\) = 2
\(\frac{400(S+10) - 400S}{S(S+10)}\) = 2
S(S+10) = 2000
on solving , S = 40 km/h
Time taken to cover 400km with usual speed ,
= \(\frac{400}{40}\)
= 10 hours