SSC CPO Maths Questions: 5th April 2020

Q1. Two trains 140 m and 160 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time (in seconds) which they take to cross each other is:
(A) 9                     (B) 9.6                   (C) 10                     (D) 10.8

Ans.- (D)           Solution :- Let S1 = 60 km/hr, S2 = 40 km/hr
                                         D1 = 140 m = 0.14 km, D2 = 160 m = 0.16 km
                                        Time = (D1 + D2)/ (S1 + S2) = (0.14 + 0.16)/ (60 + 40)
                                        Time = 0.3/100 hr = (0.3/100) * 3600
                                         => Time = 10.8
Q2. A train speeds past a pole in 15 seconds and a plateform 100 m long in 25 seconds. Its
Length is:
(A) 50 m                      (B) 150 m                  (C) 200 m                 (D) Data inadequate
Ans.-  (B)   Solution :-  Let length of train = x
                                    Speed of train is = x/15
                                    Length = Speed * Time
                              => 100 + x = (x/15) * 25
                               => x = 150 meters.
Q3. A train 110 meters long is running with a speed 60 kmph. In what time will it pass a man?
Who is running at 6 kmph in the direction opposite to that in which the train is going?
(A) 5 sec                     (B) 6 sec                     (C) 7 sec                   (D) 10 sec
Ans. - (B)   Solution: -     Let S1 = 6 kmph, S2 = 60 kmph
                                     Avg. speed = 60 + 6 = 66 kmph = 66*5/18 = 55/3 m/sec
                                     L2 = 110 meters
                                     T = 110 / (55/3) = 6 sec.

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