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    Question

    "The boat's downstream and

    upstream speeds are 18 km/hour and 12 km/hour, respectively. A boatman takes 16 hours to cover (p + q) km upstream when the stream's speed is doubled. What is the average of p and q?"
    A 72 km Correct Answer Incorrect Answer
    B 52 km Correct Answer Incorrect Answer
    C 65 km Correct Answer Incorrect Answer
    D 44 km Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ, Let, speed of boat in still water and stream speed be x km/hour and y km/hour, respectively. So, (x + y) = 18 … (i) Also, (x – y) = 12 … (ii) Solving equation (i), and (ii), we get, x = 15 km/hour y = 3 km/hour According to question, (p + q)/(x – 2y) = 16 (p + q) = 16 × (15 – 2 × 3) = 16 × 9 = 144 km Therefore, average value of p and q = (p + q)/2 =144/2 = 72 km

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