a boat travels 30 miles up the river in the same amount of time it takes to travel 42 miles down the same river. if the current is 3 miles per hour, what is the speed of the boat in still water? in still water, the boat travels at miles per hour.

Speed is calculated as follows: speed = distance / time. Knowing the units for distance and time is necessary to calculate the units for speed.

The rate at which an object travels a certain distance can be described using the speed formula. The distance that a body travels in a certain amount of time is a common way to measure speed.

Given: A boat travels 30 miles up the river in the same amount of time it takes to travel 42 miles down the same river. The current is 3 miles per hour.

From the above information we can write,

Let, u is the boat speed in still water, then

[tex]\frac{30}{u-3} = \frac{42}{u+3}[/tex]

Taking cross multiplication,

30(u + 3) = 42(u - 3)

Solving,

30u + 90 = 42u - 126

42u - 30u -126 -90 = 0

12u = 216

u = 18

Therefore, the speed of boat in still water is, 18 miles per hour.

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