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SSC CPO 2023 PYQ — Question 139

SSC CPO - 04 Oct 2023 - Shift 2 • Quantitative Aptitude • Q139

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Two trains of lengths 200 m and 250 m are running on parallel rail tracks at speeds of 68 km/h and 50 km/h, respectively. In how much time (in seconds) will they cross each other if they are running in the same direction?

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Correct answer: A

Explanation

The correct answer is option 1 i.e. 90.

Length of first train = 200 m

Speed of first train = 68 km/h

Length of second train = 250 m

Speed of second train = 50 km/h

Relative speed of two train moving in same direction = Speed of first train - Speed of second train

The crossing time = Total length of the trainstheir relative speed{Total\ length\ of\ the\ trains}\over {their\ relative\ speed}

According to the question,

The relative speed of the trains in the same direction = Speed of first train - Speed of second train

⇒ 68 - 50 = 18 km/h

Relative speed in m/sec = Relative speed in km/h ×518\times {5\over 18}= 18×51818 \times {5\over 18} = 5 m/sec

Now, the time to cross trains each other =Total length of the trainstheir relative speed{Total\ length\ of\ the\ trains}\over {their\ relative\ speed} = (200+250)5{(200 + 250)} \over 5 = 90 sec

Hence the time taken to cross the train is 90 seconds.