Answers

2016-02-06T07:40:45+05:30
Suppose edge of cube= 10cm
if we increase it by 20%=12cm
#surface area with out increasing edge=6l^2
6 x 10^2=600cm^2
#surface area with increased edge=6l^2
6 x 12^2= 864cm^2
#increase in surface area = 864-600=264
~ %age increased in surface area = 264/600 x 100=44%
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2016-02-06T11:51:11+05:30
Hi!
Let the edge of the cube be a
Then the Surface Area(S.A) =  6 × a²
After increasing the side or the edge of the cube the side will be = a + 20% a  = 120 a/100 = (12/10) a
Now the new Surface Area ( S.A *) = 6 × (12/10 × l )²
Increase in the surface area ( i ) = S.A* - S.A = a²(216 - 150 )/25 = 66/25a² 
Percentage increase(%) = (increase in the surface area) / (Original surface area) × 100%
increase = (66/25 a²) / 6 a²   ×100%
incre = 66/( 25×6) ×100%
increase % = 11/25  × 100 %
Percentage increase is = 44 %                                     Ans.
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