Find the perimeter of a rectangle with sides 3 dm. and 5 dm.

1. If the rectangle has two unequal sides, then we can find out the value of its perimeter. To do this, first we find the value of the half-perimeter by adding two unequal sides:
3 dm + 5 dm = 8 dm.
2. Now we can find out the value of the rectangle’s perimeter, doubling the value of its semi-perimeter, we get:
8 dm * 2 = 16 dm.
Answer: we got the value of the figure perimeter equal to 16 decimetres.