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      Question

      A boat moves downstream at 45 km/h, which is (25/10) m/s

      faster than its upstream speed. If it covers (D + 24) km downstream and (D - 36) km upstream in a total of 8.5 hours, find the approximate value of β€˜D’.
      A 200 km Correct Answer Incorrect Answer
      B 179 km Correct Answer Incorrect Answer
      C 110 km Correct Answer Incorrect Answer
      D 225 km Correct Answer Incorrect Answer
      E None of these Correct Answer Incorrect Answer

      Solution

      ATQ, Upstream speed = 45 - (25/10) Γ— (18/5) = 45 - 9 = 36 km/h

      Multiply throughout by LCM of 45 and 36 β†’ LCM = 180 Or, 4 Γ— (D + 24) + 5 Γ— (D - 36) = 8.5 Γ— 180 Or, 4D + 96 + 5D - 180 = 1530 Or, 9D - 84 = 1530 Or, 9D = 1614 Or, D = 179.33Β  Approximate value: D β‰ˆ 179

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