a given rectangle has an area of 20 square feet. What is the length for various widths?
5 or 4 can be the length. And 5 and 4 can be the width.
length: 5, 4, 2, 10, etc.
width: 5, 4, 2, 10, etc.
the numbers listed above are options. Multiply the numbers.
$${\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{4}} = {\mathtt{20}}$$
And $${\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{10}} = {\mathtt{20}}$$.
there are many more, but these are commonly used. Hope it helps!
The easiest way to find the answer is to divide the answer, like Alan said, but you may think his answer is confusing, so that's why I am stating this.