Subject: General Aptitude · Chapter: Problems on Trains · Exam: · Marks: · Difficulty:
Train A passes a lamp post in 9 seconds and 700 travelling? (in seconds) meter long platform in 30 seconds. How much time [IBPS—RRB Office Assistant (Online) Exam, 2015] will the same train take to cross a platform which
(a)16
(b)18 is 800 meters long? (in seconds) [United India Insurance Co. Ltd. (UIICL)
(c)12
(d)10 Assistant (Online) Exam, 2015]
Answer
Answer (as printed): C
Explanation
Let the length of train be x m. When a train crosses a light post in 9 second the distance covered = length of train x ⇒ speed of train = 9 QUANTITATIVE APTITUDE Distance covered in crossing a 700 meter platform in 30 seconds = Length of platform + length of train x + 700 speed of train = 9 x x + 700 Speed = Distance = = 9 30 Time x x + 700 ⇒ = 3 10 ⇒ 10x = 3x + 2100 ⇒ 10x − 3x = 2100 ⇒ 7 x = 2100 2100 ⇒ x= = 300 m 7 When the length of the platform be 800 m, then time ‘T’ be taken by train to cross 800 m long platform x x + 800 = 9 T ⇒ Tx = 9x + 7200 ⇒ 300T = 2700 + 7200 ⇒ 300T = 9900 9900 ⇒T= = 33 seconds 300 63 × 5
Explanation as extracted from the printed page; notation may be imperfect.