Question

Question 31

The surface area of a cuboid formed by joining two cubes of side a face-to-face, is ___

Answer 1

$10a^2$
We have, two cubes of side a.
These two cubes are joined face-to-face, then the resultant solid figure is a cuboid which has same breadth and height as the joined cubes has length twice of the length of a cube.
i.e. l = 2a, b = a and h = a
Thus, the total surface area of the cuboid $=2(lb+bh+hl)$
$=2(2a\times a+a\times a+a\times 2a)=2(2a^2+a^2+2a^2)=2\times 5a^2=10a^2$