Perimeter is a calculation of all the outer side of the shapes .
Formula for perimeter -> Length of Outer side + length of outer side = ____cm @ m.
Let's us view another example :
The calculation for this shape is :
12cm + 10cm + 3cm + 6cm + 6cm ( 12cm - 3cm - 3cm ) + 6cm + 3cm + 10cm = 56cm .
It is really simple , is it ?
Remember ! Perimeter only uses '+' .
If the shape is square , you can multiply the length of outer side .