A rectangular portion is cut off from a rectangular sheet (figure 1) as shown in figure 2. Find the perimeter of the sheet shown in figure 2.
If we just consider the boundary of the sheet, it is easy to observe that the part of the sheet cut off decreases the area but length of the boundary remains same as shown below.
Therefore, the perimeter of the sheet in figure 2 will be equal to the one in figure 1. The areas, on the other hand, will be different.
P = 2(l + b) = 2(6 + 4) = 20 m
From figure 2,
perimeter, P = [6 + 4 + (6 - 1.5) + (4 - 1) + 1.5 + 1] m = 20 m