# A boat going upstream takes 1.5 times longer than going the same distance downstream. If the water current in the river is 8 kph, calculate the speed of the boat in still water.

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**Problem**

A boat going upstream takes 1.5 times longer than going the same distance downstream. If the water current in the river is 8 kph, calculate the speed of the boat in still water.

A. 30 kph | C. 40 kph |

B. 50 kph | D. 20 kph |

**Answer Key**

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[ C ]

**Solution**

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$t_\text{go upstream} = 1.5 \, t_\text{go downstream}$

Let *x* = speed of the boat in still water and *d* = distance

$\dfrac{d}{x - 8} = 1.5 \left( \dfrac{d}{x + 8} \right)$

$x + 8 = 1.5(x - 8)$

$0.5x = 20$

$x = 40 ~ \text{kph}$ ← *answer*

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