**Question:**

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

**Solution:**

10a2

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= aandh = a

Thus, the total surface area of the cuboid = 2 (lb + bh + hi)

= 2 (2a x a + a x a + a x 2a)

= 2 (2 a2 + a2 + 2 a2)=2 x 5 a2 = 10a2