Q2 of 24 Page 145

Find the volume of a cube whose surface area is 486 cm2.

Given: Surface Area of a Cube = 486 cm2

So, firstly we find the side of a cube


Total Surface Area of a Cube = 486 = 6a2



a2 = 81


a = = ± 9 = 9cm (side can’t be negative)


Therefore, Side of a cube = 9 cm


Now, Volume of a Cube = a3 = (9)3 = 9 × 9 × 9 = 729 cm3


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(i) Which box has a smaller total surface area?


(ii) If each edge of the cube is doubled, how many times will its T.S.A increase?

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