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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 Γ— (15 – 2 Γ— 3) = 16 Γ— 9 = 144 km Therefore, average value of p and q = (p + q)/2 =144/2 = 72 km

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