A train moving at a uniform speed covers 36km in 21 minutes. How long does it take to cover 60km?

A.
35 mins 
B.
40 mins 
C.
45 mins 
D.
90 mins
Correct Answer: Option A
Explanation
Since 36km in 21 minutes
1km in (frac{21}{36})minutes
60km in (left(frac{21}{36}times 60right))minutes = (frac{70}{2})min
= 35 mins