Perimeter and area of a rectangle

How to use it

1. 1Halve the perimeter first: $\frac{P}{2}=l+b$ is the sum of the two dimensions, and the area is their product.
2. 2Given the perimeter and the area, $l$ and $b$ are the two roots of $t^2-\frac{P}{2}t+A=0$.
3. 3Scaling both dimensions by a factor $k$ scales the perimeter by $k$ and the area by $k^2$.

Step-by-step

1. 1
   $P=2(9+4)=26$ cm
2. 2
   $A=9\times 4=36$ cm${}^2$