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Example J.2: Circumference of a table

If our table is 1.80 m in length and 1.20 m in width and has the shape of a rectangle, what is its circumference (or perimeter)? We might want to glue a ribbon around the edge, and we want to know how long it has to be.

Solution

First we write down what we know, giving it names that remind us what the values are about:

\(L_{\mathrm{table}}\) \(= 1.80\ \mathrm{m}\)


\(W_{\mathrm{table}}\) \(= 1.20\ \mathrm{m}\)


Then we write down what we are planning on calculating. Here, it is the perimeter
\(\mathrm{perimeter}\) = ?


Now we make a plan. The perimeter of a rectangle is equal to its twice its length \(L\) plus twice its width \(W\) . The formula would be:


Finally, we can ask PQcalc to do the calculation for us:

\(\mathrm{perimeter}\) \(= 2 \cdot L_{\mathrm{table}} + 2 \cdot W_{\mathrm{table}}\)

\(\ \ \ =2 \cdot 1.80\ \mathrm{m} + 2 \cdot 1.20\ \mathrm{m}\)

\(\ \ \ =3.600\ \mathrm{m} + 2.400\ \mathrm{m}\)

\(\ \ \ =6.00\ \mathrm{m}\)


The table has a perimeter of 6.00 meters.