This is simple with any shapes .
Perimeter is equal to the sum of all sides.
In this case the length and breadth is given, this is a rectangle.
So the other 2 sides remaining is an exact replica of these sizes β90 and 45β
So the sides are β 90, 90, 45, 45β respectively.
The perimeter thus is sum of all of these
= (90 + 90) + (45 + 45)
=180 + 90
Perimeter is = 180 + 90
Thus 270m