# In still water, your small boat average 8 miles per hour. It takes you the same amount of time to travel 15 miles downstream, with the current, as 9 miles upstream, against the current. What is the rate of water's current?

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**Problem**

In still water, your small boat averages 8 miles per hour. It takes you the same amount of time to travel 15 miles downstream, with the current, as 9 miles upstream, against the current. What is the rate of water's current?

A. 4 miles/hr | C. 2 miles/hr |

B. 3 miles/hr | D. 5 miles/hr |

**Answer Key**

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[ C ]

**Solution**

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Let

$t_\text{15 miles going downstream} = t_\text{9 miles going upstream}$

*y*= rate of the water-current$t_\text{15 miles going downstream} = t_\text{9 miles going upstream}$

$\dfrac{15}{8 + y} = \dfrac{9}{8 - y}$

$y = 2 \text{ mph}$ ← *answer*

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