To arrive on schedule, a train is to cover a distance of 60km at 72km/hr….

Correct Answer: Option C

Explanation

(speed = frac{distance}{time}\
72 = frac{60}{time}\
t = frac{60}{72} = frac{5}{6}hr)
time lost = 10mis (= frac{10}{60}hr = frac{1}{6})
Time required for the journey
(=frac{5}{6}-frac{1}{6} = frac{2}{3}\
speed hspace{1mm}=60 div frac{2}{3} = 90km/hr)