In Algebra 2, we may be asked to look at rates. Often these come in the form of speed and distance questions. The general formula for this type of problem is . Here is an example problem:
A man can row at in still water. The speed of the river he now rows in is
. How long will it take him to row upstream
?
Using the formula we will rearrange it to solve for time. Now,
. Our distance is a 30 km and our rate is his speed in stillwater minus the current speed. So,
. Simplifying,
. Finally, time equals 15 hours.

Oar propelled ship. Abraham Willaerts (circa 1603–1669).
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