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    Question

    The speed of boat downstream and upstream is 30 km/hr

    and 20 km/hr respectively. Time taken to travel a distance of (a + 50) km downstream and (b + 25) km upstream is 12 hours, and time taken to travel (a + 90) km upstream and (b + 70) km downstream is 18 hours. Find the difference between the value of a and value of b.
    A 25 Correct Answer Incorrect Answer
    B 30 Correct Answer Incorrect Answer
    C 20 Correct Answer Incorrect Answer
    D 15 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    According to question, (a+50)/30+(b+25)/20=12 (2a+100+3b+75)/60=12 2a+3b=720–175=545 … (iii) Also, (a+90)/20+(b+70)/30=18 (3a+270+2b+140)/60=18 3a+2b=1080–410=670 … (iv) Solving equation (iii) and (iv), we get, a=125 and b=95 Therefore, required difference = 125 – 95 = 30

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