Question 1031402
x = original side length


side length increases by 20% so
x+0.2x = 1.2x
is the new side length


new area
(1.2x)(1.2x) = (1.2*1.2)*(x*x) = 1.44x^2


Old area
x*x = x^2


Subtract the areas
1.44x^2 - x^2 = 0.44x^2


So the new area is 44% bigger compared to the old area. 


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Example:
Old side length = 10 ---> old area = 10*10 = 100
New side length = 10*1.2 = 12 ---> new area = 12*12 = 144
Difference in areas = new - old = 144 - 100 = 44
Divide the difference by the old amount to get 44/100 = 0.44 = 44%