# Thread: Surface area of cube

1. ## Surface area of cube

Two cubes have volumes in the ratio 1:27.the ratio of their surface areas is
(a)1:3
(b)1:8
(c)1:9
(d)1:18

2. Originally Posted by devi
Two cubes have volumes in the ratio 1:27.the ratio of their surface areas is
(a)1:3
(b)1:8
(c)1:9
(d)1:18
For a cube of 1 unit length, it's volume is 1. For a cube of side length 3 units, its volume is $3^3=27units^3$.

So their side lengths are in the ratio 1:3.

The surface area of a cube is given by $6\times length^2$.

So the surface areas will be 6 and 54. Since 54 is 9 times 6, the ratio of their surface areas will be 1:9.

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# Two cubes have their volumes in the ratio 1:27. Find the ratio of their surface areas

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