What will be increase in the volume of cuboid if length breadth and height of the cuboid are in the ratio 1 is to 2 is to 3?

Cuboid is a solid box whose every surface is a rectangle of same area or different areas.

A cuboid will have a length, breadth and height.Hence we can conclude that volume is 3 dimensional. To measure the volumes we need to know the measure 3 sides.

Since volume involves 3 sides it is measured in cubic units.

Volume of a cuboid = (length × breadth × height) cubic units.= (l × b × h) cubic units.

(Since area = ℓ × b)

Volume of a cuboid = area of one surface × height cubic units

Let us look at the given cuboid.

The length of the cuboid = 5 cm

The breadth of the cuboid = 3 cm

The height of cuboid (thickness) = 2 cm

The number of 1 cm cubes in the given cuboid = 30 cubes = 5 × 3 × 2

We find that volume of the given cuboid with length 5 cm, breadth 3 cm and height 2 cm is 30 cu cm.

Therefore, volume of a cuboid = length × breadth × height

Solved examples on volume of a cuboid:

1. Find the volume of a cuboid of dimensions 14 cm × 12 cm × 8 cm.

Solution:

Volume of cuboid = length × breadth × height. Here, length = 14 cm, breadth = 12 cm and height = 8 cm.Volume of cuboid = 14 × 12 × 8 cubic cm.= 1344 cubic cm.

Therefore, volume of cuboid = 1344 cubic cm.

2. Michael made a shoe box with length 8 cm, breadth 6 cm and height 6 cm. Find the volume of the box.

Solution:

Volume of the shoe box = Length × breadth × height.

= 8 × 6 × 6

= 288 cu cm.

3. A fish tank is 40 cm long, 15 cm broad and 10 cm high. What is its volume in cu cm?

Solution:

The length of the fish tank = 40 cm

The breadth of the fish tank = 15 cm

The height of the fish tank = 10 cm

Therefore, the volume of the fish tank = length × breadth × height.

= 40 × 15 × 10 cu. cm

= 6000 cu cm.

4. Find the volume of a cuboid of dimensions 14 cm × 50 mm × 10 cm.

Solution:

Here, length = 14 cm,

[Given, breadth = 50 mm; we need to convert breadth to same unit and then solve. We know, 10 mm = 1 cm. Therefore, 50 mm = 50/10 cm = 5 cm].

Breadth = 5 cm, Height = 10 cm.

Volume of cuboid = length × breadth × height. = 14 × 5 × 10 = 700 cubic cm.Therefore, volume of cuboid = 700 cubic cm.

Note: In a cuboid, when the length, breadth and height are of different units, convert them to a same unit and then solve.

5. Find the volume of a cuboid of dimensions 17 mm × 0.2 cm × 12 mm in cu. cm.

Solution:

Given, length = 17 mm. We know, 10 mm = 1 cm.= 17/10 cm. = 1.7 cm.Therefore, length = 1.7 cm.

Similarly, height = 12 mm.We know, 10 mm = 1 cm.= 12/10 cm.= 1.2 cm.Therefore, height = 1.2 cm.

Volume of cuboid = length × breadth × height.Length = 1.7 cm, breadth = 0.2 cm and height = 1.2 cm. = 1.7 × 0.2 × 1.2 cu. cm. = 0.408 cu. cm.Therefore, volume of cuboid = 0.408 cubic cm.

6. Find the number of cubical boxes of cubical side 3 cm which can be accommodated in carton of dimensions 15 cm × 9 cm × 12 cm.

Solution:

Volume of box = side × side × side. = 3 × 3 × 3 = 27 cu. cm.Volume of carton = length × breadth × height. = 15 × 9 × 12 = 1620 cu. cm.Number of boxes = Volume of carton/Volume of each box. = 1620/27 = 60

Therefore, number of cubical boxes = 60.

7. How many bricks each 25 cm long, 10 cm wide and 7.5 cm thick will be required for a wall 20 m long, 2 m high and 0.75 m thick? If bricks sell at $900 per thousand what will it cost to build the wall?

Solution:

Volume of the wall = 20 m × 2 m × 0.75 m

= 20 × 100 cm × 2 × 100 cm × 0.75 × 100 cm

Volume of brick = 25 cm × 10 cm × 7.5 cm

Number of bricks = Volume of the wall/Volume of the brick

= 20 × 100 × 2 × 100 × 0.75 × 100/25 × 10 × 7.5

= 16000

The number of bricks = 16000

The cost of 1 thousand bricks = $ 900

The cost of building the wall = $ 900 × 16 = $ 14400

Note: While calculating the volume of a cuboid all the dimensions should be changed into the same unit.

Questions and Answers on Cuboid:

1. Find the volume of each of the cuboids.

(i) Length = 5 cm, Breadth = 4 cm and Height = 3 cm

(ii) Length = 15 m, Breadth = 10 m and Height = 2 m

(iii) Length = 0.5 m, Breadth = 3 m and Height = 4 m

(iv) Length = 3.2 cm, Breadth = 2 cm and Height = 8 cm

(v) Length = 5 m, Breadth = 1.5 m and Height = 1.2 m

Answers:

1. (i) 60 cu cm

(ii) 300 cu m

(iii) 6 cu m

(iv) 51.2 cu cm

(v) 9 cu m

2. Find the volume of these tanks.

(i) Length = 16 cm, Breadth = 60 cm and Height = 20 cm

(ii) Length = 6 m, Breadth = 3 m and Height = 5 m

(iii) Length = 2 m, Breadth = 1.5 m and Height = 1.5 m

(iv) Length = 80 cm, Breadth = 20 cm and Height = 40 cm

(v) Length = 1.2 m, Breadth = 1.2 m and Height = 1 m

Answers:

2. (i) 19200 cu cm

(ii) 90 cu m

(iii) 4.5 cu m

(iv) 64,000 cu cm

(v) 1.44 cu m

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