total number of cards: 12 + 27 + 91 = 130
total number of cards with a circle: 91
so you have a 91/130 probability which reduces to 7/10 probability
The formula required is tangent
2 steering wheels manufactured each hour were defected
There were 50 steering wheels manufactured per hour
The fraction is

Divide 2, which is the numerator by 50, which is the denominator
2÷50=.04
To change any decimal into a fraction, multiply by 100
The multiply .04 by 100 to change into a percentage
.04×100=4.⇒4%
4% is the percentage of defective steering wheels
The radius is equal to the side of the polygon. The 20-gon has 20 sides.
let n = number of sides of the polygon
A = area of the polygon
s = measure of one side of the polygon
a = apothem
a = s / (2tan(180/n))
a = 9mm / (2tan(180/20))
a = 28.41 mm
P = s * n
P = 9mm * 20
P = 180 mm
A = a * P / 2
A = 28.41 mm * 180 mm / 2
A = 2556.9 mm^2