If radius of a circle is diminished by 10% then its area is diminished by
10%
19%
20%
36%
Explanation:
Let, the old radius be `r`.
New r=(100-10)/100= 0.9r.
Old area=3.14 $\times$ $r^2$
New area=3.14 $\times$ $0.81r^2$
Hence, % decrease= [3.14 $r^2$(1-0.81)] $\times$ 100/3.14 => $r^2$ = 19%.