Which shows the correct expression for finding the volume of the composite figure above? A. (7x15x5)+(1/2x3x7)
B. (7x12x5)+(1/2x3x7)
C. (7x15x5)+(1/2x3x7x5)
D. (7x12x5)+(1/2x3x7x5)

C

Step-by-step explanation:

area of part 1:

a1=base*height/2=(8+2)*(8-2-2-1)/2=10*3/2=15 ft^2

area of part 2:

a2=length*width=(8+2)*1=10 ft2

area of part 3:

a3=length*width=8*2=16 ft2

total shaded area : a1+a2+a3=41 ft2

total area of the reactangle : a=16*8=128 ft2

total area of the nonshaded region : 128-41=87 ft2