area of circle: πr^2
area of square: l * w (or l * l)
16.
we are looking for the area of the larger circle with the area of the tiny circle in the middle.
to start we can find the area of the larger circle.
the radius is half the diameter, so r=6.
π(6^2) = 113.04
next we should find the area of the tiny circle.
8/2 = 4; r = 4
π(4^2) = 50.24
so to find the area of the shaded parts, we can subtract the area of the big circle with the tiny one.
113.04 - 50.24 = 62.8m^2
17.
now we are looking for the area of a square minus the area of the circle inside
let's find the area of the square
5.25 * 5.25 = 27.5625
next the circle,
the diameter is 5.25, so r= 2.625
π(2.625^2) = 21.6365625
finally we subtract the area of the square with that of the circle
27.5625 - 21.6365625 = 5.9259375 or
5.9in^2
18.
now we are looking for the area of a circle minus 2 tiny ones inside of it.
area of big circle:
12.5/2 = 6.25
π(6.25^2) = 122.65625
area of tiny circle:
1.5/2 = 0.75
π(0.75^2) = 1.76625
finally we do area of big circle minus 2 of the tiny circles
122.65625 - 2(1.76625) = 119.12375 or
119.1cm^2