Question
A boat, whose speed in still water is 25% more than the
speed of the current, covers 810 km downstream in _____ hours. The speed of the boat in still water is ______ km. The values given in which of the following options will fill the blanks in the same order in which is it given to make the statement true: I. 10, 45 II. 15, 30 III. 12, 35.7Solution
Let, the speed of the current be x km/hr Therefore, speed of the boat in still water = 1.25x km/hr Downstream speed of the boat = x + 1.25x = 2.25x km/hr For I: 2.25x = 810/10 => 2.25x = 81 => x = 36 Therefore, speed of boat in still water = 1.25x = 45 km/hr Therefore, I is True. For II: 2.25x = 810/15 => 2.25x = 54 => x = 24 Therefore, speed of boat in still water = 1.25x = 30 km/hr Therefore, II is true. For III: 2.25x = 810/12 => 2.25x = 67.5 => x = 30 Therefore, speed of the boat in still water = 1.25x = 37.5 km/hr Therefore, III is false.
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