What is the approximate perimeter of trapezoid defg

Sides GF and DE are easy to measure. Just count units.
GF = 5
DE = 3

Sides DG and EF need a little calculation.
Think of side DG as the hypotenuse of a right triangle whose legs measure 1 and 2 units. Using the Pythagorean theorem, we can find the lengths of DG and EF.

2^2 + 1^2 = DG^2

4 + 1 = DG^2

5 = DG^2

DG = sqrt(5)

Perimeter = 5 + 3 + sqrt(5) + sqrt(5)

Perimeter = 8 + 2sqrt(5)

Perimeter is approximately 12.5 units