CMAT 2019 Solved Question Paper

Question : 24 of 100

Marks: +1, -0

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

$729 cm^2$
$486 cm^2$
$125 cm^2$
$529cm^2$

Validate

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

⇒a=9\cm

Surface area of cube so formed

= 6×a^2=6×9^2=486cm^2

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