Question 1004275
Hi there,
The area of a circle is directly 
proportional to the square of its radius.
A = kr^2
Where k = constant of proportionality
A = kr^2
1256 = k20^2
k = 1256/400
k = 3.14
Formula:
A = 3.14r^2
Problem:
A = 3.14 x 10^2
A = 3.14 x 100
A = 314 sq cm.
Hope this helps :-)