Given: Speed of train A = 150% of Speed of train B Calculations: Time taken by train A= Ta Time taken by train B= Tb ⇒ Tb – Ta = 15 minutes …(i) If train A takes ‘Ta’ time to travel a distance, it will take ‘2Ta’ time to travel double the distance ⇒ 2Ta – Tb = 18 minutes …(ii) Adding (i) and (ii), ⇒ Ta = 33 minutes ∴ The train A will cover the distance in 33 minutes Shortcut Trick A takes 15 min less time than B to cover the distance. B takes 15 min more than A to complete the distance. If A covered double the distance when B covers the same distance as earlier then A takes 18 minutes more than B. So, A 's time taken to cover the double distance = 15 min (as A completed the distance 15 min earlier than B) + 18 min = 33 min So total time taken by A to cover the double distance = 15 + 18 = 33 minutes