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After sailing 18 mi, a sailor changed direction and increased the boat's speed by 4 mph. An additional 13 mi was sailed at the increased speed. The total sailing time was 3 h. Find the rate of the boat for the first 18 mi.

Solution

Solution

trip 1 speed : 9

trip 2 speed : 13

Solution steps

Translate the problem into an equation:

\frac{18}{x} + \frac{13}{x + 4} = 3

Solve for

x, \frac{18}{x} + \frac{13}{x + 4} = 3 : x = 9, x = - \frac{8}{3}

Find speed

trip 1 speed : 9

trip 2 speed : 13

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