Subject: General Aptitude · Chapter: Problems on Trains · Exam: · Marks: · Difficulty:
What is the speed of a train if it overtakes two (M.A.T., 2005, SNAP, 2010) persons who are walking in the same direction
(a)48 km/hr
(b)54 km/hr at the rate of a m/s and (a + 1) m/s and passes
(c)66 km/hr
(d)82 km/hr them completely in b seconds and (b + 1) seconds respectively? (C.D.S., 2004)
Answer
Answer (as printed): B
Explanation
Let the length of the train be x metres and its speed be y m/s. x x Then, = b and = (b + 1) y–a y – ( a + 1) ⇔ x = b (y – a) and x = (b + 1) (y – a – 1) ⇔ b (y – a) = (b + 1) (y – a – 1) ⇔ by – ba = by – ba – b + y – a – 1 ⇔ y = (a + b + 1).
Explanation as extracted from the printed page; notation may be imperfect.