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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. 18, 23

II. 12, 37.5

III. 18, 30

A only I and II Correct Answer Incorrect Answer
B only II and III Correct Answer Incorrect Answer
C only II Correct Answer Incorrect Answer
D All are true Correct Answer Incorrect Answer
E only III Correct Answer Incorrect Answer

Solution

Downstream speed of the boat = x + 1.25x = 2.25x km/hr For I: 2.25x = 810/18 => 2.25x = 45 => x = 20 Therefore, speed of boat in still water = 1.25x = 25 km/hr Therefore, I is false. For II: 2.25x = 810/12 => 2.25x = 67.5 => x = 30 Therefore, speed of boat in still water = 1.25x = 37.5 km/hr Therefore, II is true. For III: 2.25x = 810/18 => 2.25x = 45 => x = 20 Therefore, speed of the boat in still water = 1.25x = 25 km/hr Therefore, III is false.

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