Beginning algebra: writing equations for word problems

We look at four different word problems and write an equation for each. The first one involves the perimeter of a parallelogram. The second, area of a two-part rectangle. The third one has to do with the ages of two people — we know one is four times as old as the other, and 40 years older than the other. In the last problem, we're given the aspect ratio and the perimeter of a rectangle, and the task is to find the side lengths.

For each problem, write a fairly simple linear equation and then solve the equation. I also solve some problems without the equation first — so you can see how the mental math or bar diagram solution steps match with the steps of solving the equation.

See also

How to use the formula for distance, rate (speed), and time to solve problems

Variable on both sides — video lesson

Math Mammoth Grade 7 curriculum (pre-algebra)

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