Answer:
28 +8√5 ≈ 45.89 cm
Explanation:
You want the perimeter of an isosceles trapezoid with bases 10 and 18 cm and height 8 cm.
Slant height
The length of each side of the trapezoid is the hypotenuse of a right triangle with legs 4 and 8:
c² = a² +b²
c² = 4² +8² = 16 +64 = 80
c = √80 = 4√5 . . . . . . length of one side of the trapezoid
Perimeter
The perimeter is the sum of the lengths of the sides and the bases:
10 + 18 + 2(4√5) = 28 +8√5 . . . . . cm
The perimeter is 28 +8√5 ≈ 45.89 cm.