Question 1069459
Let say the side of the square is {{{s}}}.
The area is then {{{A[1]=s^2}}}.
Increasing the side by 10% makes the side {{{(1+10/100)s=1.1s}}}
So the area is now {{{A[2]=(1.1s)^2=1.21s^2}}}
So then,
{{{((A[2]-A[1])/A[1])*100=((1.21s^2-s^2)/s^2)*100=21}}}
21% increase