Question

The edge of cube is increased by 50 % then increased in its surface area will be

Answer 1

let the length of the edge of a cube be'a cm'
original area of cube = 6 a^2

Given that if edge of cube increased by 50% :
then find new length of edge :
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new length of edge = ( a + 50% of a)cm

= a + 0.5 a = 1.5 a cm

new area of cube = 6 ( 1.5 a )^2

= 6 × 2.25 a^2 = 13.5 a^2

increase in surface area of the cube

= new area of cube - original area of cube

= 13.5 a^2 - 6a^2 = 7.5 a^2

increase%= increase ×100/original area

= 7.5 a^2 / 6a^2 × 100

= 7.5 × 100 / 6 = 125 %

therefore , surface area of the cube will be increased by 125 %.
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Your Answer : 125 %
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shortcut method:
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let increase in the edge of cube a=50

increase in surface area will be

= a + a + ( a × a / 100 )

=50 + 50 + ( 50 × 50/100 )

=100 + 2500/100

=100 + 25 = 125 %
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