Subject: General Aptitude · Chapter: Problems on Trains · Exam: · Marks: · Difficulty:
What is the speed of train? (Bank P.O. 2004) I. The train crosses a signal post in 20 seconds. II. The train crosses a 260 metre long platform in 33 seconds. III. The train crosses another stationary train of same length in 40 seconds.
(a)Only I and II
(b)Any two of the three
(c)All I, II and III
(d)II and either I or III
(e)Even with all three statements answer cannot be given. is followed by three statements. You have to study the question and all the three statements given to decide whether any information provided in the statement(s) is redundant and can be dispensed with while answering the given question.
Answer
Answer (as printed): D
Explanation
Let the length of the train be x metres and its speed be y m/sec. x From I, we have: = 20 ...(i) y x + 260 From II, we have: y = ...(ii) 33 2x x ) From III, we have: y = or = 20 ...(iii) 40 y Thus, the value of y can be found by solving (ii) with either (i) or (iii) simultaneously. II and either I or III together give the answer. Hence, the correct answer is (d).
Explanation as extracted from the printed page; notation may be imperfect.