The perimeter is the total distance around a shape, starting and finishing at the same point.
Here the perimeter is 1 + 2 + 1 + 1 + 2 + 3 = 10 cm
Remember that the area of rectangle is it's length x it's width.
If we know the area and one side, we can divide to find the length of the other side.
A rectangular room has an area of 12 m2
If it's length is 4 m, what is it's width?
We divide 12 ÷ 4 = 3
So width = 3 m