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SSC MTS 2022 PYQ — Question 68

SSC MTS - 26 July 2022 - Shift 2 • Quantitative Aptitude • Q68

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A man rows from A to B (upstream) and B to A (downstream) in 12 hours. The distance between A and B is 240 km. The time taken by the man to row 6 km downstream is identical to the time taken by him to row 4 km upstream. What is the speed of the stream?

Show answer & explanation

Correct answer: D

Explanation

The correct answer is option 4 i.e. 25/3 km/h

Let the speed of the boat is x km/h and speed of the stream is y km/h - 

So,

Speed downstream = (x + y) km/h

Speed upstream = (x - y) km/h

Now,

According to the question - 

6(x+y)=4(x−y)\frac{6}{(x+y)}=\frac{4}{(x-y)}

6(x - y) = 4(x + y)

6x - 6y = 4x + 4y

2x = 10y

x = 5y 

So,

Speed downstream = 5y + y = 6y km/h

Speed upstream = 5y - y = 4y km/h

Now,

2406y+2404y=12\frac{240}{6y}+\frac{240}{4y}= 12

40y+60y=12\frac{40}{y}+\frac{60}{y}= 12

100y=12\frac{100}{y}=12

y=10012y=\frac{100}{12}

y=253y=\frac{25}{3} km/h