Q10 of 20 Page 111

The length of each arm of a square was increased by 10%. Let’s work out the increase of the percentage of area by the Rule of Three.

Given: percentage increment of each arm of the square.


Tip:(i) if y is increased by x% then the new value of y is



(ii) Increment percentage


Let us assume that the length of each arm of the square is "a" unit length.


Using tip (i)


We calculate the new value of the arms of the square.


Therefore, the new value of the arms of the square is




We know area of square = side × side


The area of the square when the arm length was “a “units = a× a = a2 unit square.


The area of the square when the arm length has changed to unit is



Therefore, the increment of the area is




Therefore, the increment percentage is:




=21%


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