To find r, you need to isolate it. pi*r^2*60=18,840. divide 18,840 by 60, then pi, it comes out at 100. Now find the square root to get 10
r=10
% change = change × 100/ initial
= 10×20/100
= 2 %
The answer is 2%
144 = 1 x 144, 2 x 72, 3 x 48, 4 x 36, 6 x 24, 8 x 18, 9 x 16, 12 x 12. Factors of 144: 1, 2, 3, 4, 6, 8, 9, 12, 16, 18, 24, 36, 48, 72, 144.