Hello Nicole,
There are two ways to do this type of problem. The first way would be to create a system of equations to figure out the dimensions. However, for an elementary level problem, this method is too difficult. The second way would be to simply guess and check until we pick the right numbers.
We know that the perimeter of the rectangle is 28m, meaning all sides add up to 28. In a rectangle, we know that the 2 long sides have the same value (the length-L) and the 2 shorter sides have the same value (the width-W). The problem also states that the length times the width, or the area, is 24m^2.
So we know we are looking for two numbers that when multiplied together equal 24 and when added according to the perimeter equation (2L + 2W) equals 28.
First, let's list all the ways we can multiply to get a value of 24:
1 x 24
2 x 12
3 x 8
4 x 6
These are now our possible lengths and widths of the rectangle. Now, we must see which sets of numbers add to a perimeter of 28.
(2x24) = 2 + 48 = 50
(2x2) + (2x12) = 4 + 24 = 28
(2x3) + (2x8) = 6 + 16 = 22
(2x4) + (2x6) = 8 + 12 = 20
So the length of our rectangle is 12m and the width is 2m.
I hope this helps!