If radius of a circle is increased by 10%, then its area would increase by:

100% 20% 21% 19%

21%

Apply successive formula Y + Y + \(\frac{Y \;×\; Y}{100}\) = 10 + 10 + \(\frac{10\;×\; 10}{100}\) = 21% Therefore, the percentage increase in its area is 21%.