From a circular sheet of paper with a radius of 20 cm, four circles of radius 5cm each are cut out. What is the ratio of the paper left to the area of the circles?
Area of the circular sheet = $\pi$ * (20)2 = 400 $\pi$
Area of 4 smaller circles cut out = 4 * $\pi$ * (5)2 = 100 $\pi$
So, area of remaining paper = 300 $\pi$
$\therefore$ Ratio of the paper left to the area of the circles = 300 $\pi$ : 100 $\pi$ = 3 : 1
C is the answer.