Exams › IBPS PO › Quantitative Aptitude

The ratio of the speed of a boat in still water to the speed of the current is 4:1. The total time taken by the boat to cover D km downstream and \(D-10\) km upstream is 12 hours. Find \(D\).

1. 125
2. 105
3. 80
4. Can't be determined

Correct answer: Can't be determined

Solution

Let the speed of current be \(c\), then still-water speed is \(4c\). Downstream speed = \(5c\) and upstream speed = \(3c\), so the time equation becomes \(\frac{D}{5c}+\frac{D-10}{3c}=12\), which contains both \(D\) and \(c\). Since there is only one equation for two unknowns, \(D\) cannot be uniquely determined.

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