Missing Side From Rectangle Area

Find the missing side of a rectangle

If you know a rectangle’s area and one side length, you can find the missing side by using the area relationship:

Area = length × width

So the missing side is found by dividing the area by the known side.

Method

1. Write the area equation: (A = l \times w).
2. Substitute the known values.
3. Divide the area by the known side to isolate the missing side.
4. Simplify the result completely.

Example pattern

If the area is 48 and one side is 6, then: [ 48 = 6 \times x ] [ x = 48 \div 6 = 8 ] So the missing side is 8.

Check your answer

Multiply the two side lengths together. If the product equals the given area, your answer is correct.

Important idea

Use the same units for both side lengths, and remember that the answer for a side length should be written in units, such as cm, m, or in.