The ratio of the radii of two circle is 1:3 the radio of their areas is?

• A. None of these
• B. 1:3
• C. 1:9
• D. 1:6

Answer: (C)

The Radio of areas = area of first circle : area of 2nd circle= ?r2 / ?(3r)2= ?r2/ 9 ?r2= 1/9 = 1: 9