NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.1 – Part 2
Q4 The paint in a certain container is sufficient to paint an area equal to . How many bricks of dimensions can be painted out of this container?
Solution:

The container can paint an area

Dimensions of brick
Therefore, total surface area of a brick
Number of bricks can be painted =
Q5 A cubical box has each edge and another cuboidal box is long, wide and high.

Which box has the greater lateral surface area and by how much?

Which box has the smaller total surface area and by how much?
Solution:

Cubical box has each edge

Length

Width

Height
Lateral surface area is the area of the faces along the height. That is, it is the area excluding the top and bottom. Now for cube this would be the area of any 4 faces. For the cuboid it would be
Solution (i)

Lateral surface area of cubical box of edge

Lateral surface area of cuboid box is

Thus, lateral surface area of the cubical box is greater by
Total surface area of cubical box of edge
Total surface area of cuboidal box
=
=
=
So, total surface area of cubical box is smaller by