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 ‘D’.Solution
ATQ, Upstream speed = 45 - (25/10) × (18/5) = 45 - 9 = 36 km/h Multiply throughout by LCM of 45 and 36 → LCM = 180 Or, 4 × (D + 24) + 5 × (D - 36) = 8.5 × 180 Or, 4D + 96 + 5D - 180 = 1530 Or, 9D - 84 = 1530 Or, 9D = 1614 Or, D = 179.33 Approximate value: D ≈ 179
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