A train covers 252 km at a uniform speed. If the speed had been 15 km/h more, it would have taken 5 hours less for the same journey. What is the speed of the train (in km/h)?
Answer & explanation
Correct answer: option 3
D = [\(\frac{S_1 × S_2}{Diff. (S_1\;and\;S_2)}\)] × Time (Diff.)
Let initial speed = S
Increased speed = S + 5
252 = \(\frac{S × (S + 15)}{15}\) × 5
S (S + 15) = 252 × 3
S (S + 15) = 21 × 36
⇒ S = 21 km/h