Question 24

Three solid cubes of sides 1 cm, 6 cm and 8 cm are melted to form a new cube. Find the surface area of the cube so formed.

Solution

Whenever some cubes are melted to form a single larger cube, the total volume always remains constant.

So, Sum of the volumes of three small cubes = Volume of the larger cube.

Let the side of the lager cube so formed be 'a' cm.

Then $$1^3 + 6^3 + 8^3 = a^3$$

$$\Rightarrow a^3 = 729$$

$$\Rightarrow a = 9$$ cm.

Surface area of cube so formed = 6*$$a^2$$ = $$6\times 9^2 = 6\times 81 = 486  cm^2$$

Video Solution

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