Question

How to solve for shaded area

Answer 1

Answer:

(a)  12.96 ft²

(b)  21.5 in²

Step-by-step explanation:

(a) For the first diagram

Area of the shaded region (A) = Area of Tripezium- area of circle

A = [1/2(a+b)h]-[πr²]............... Equation 1

Where a and b are the parallel side of the tripezium respectively, h = height of the tripezium, r = radius of the circle.

From the diagram,

Given: a = 15 ft, b = 6 ft, h = 12 ft, r = h/2 = 12/2 = 6 ft.

Constant: π = 3.14

Substitute these values into equation 1

A = [12(15+6)/2]-(3.14×6²)

A = 126-113.04

A = 12.96 ft²

(b) For the second diagram,

Area of the shaded region (A') = Area of square- area of circle

A' = (L²)-(πr²)............. Equation 2

Where L = lenght of one side of the square, r = radius of the circle

From the diagram,

Given: L = 2r = (2×5) = 10 in, r = 5 in

Substitute these values into equation 2

A' = (10²)-(3.14×5²)

A' = 100-78.5

A = 21.5 in²