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Surface Areas and Volumes - Volume of a Cuboid and Cube

Grade 9CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Volume refers to the amount of three-dimensional space occupied by an object. Visually, you can think of volume as the number of unit cubes (cubes with side 11 unit) that can fit perfectly inside a solid without leaving any gaps.

A cuboid is a solid figure bounded by six rectangular faces. Visually, it has three distinct dimensions: length (ll), breadth (bb), and height (hh). Imagine a rectangular shoe box; the area of the base is l×bl \times b, and when you stack multiple such rectangular layers up to a height hh, you get the volume.

A cube is a special case of a cuboid where all three dimensions are equal. Visually, every face of a cube is a square of the same size. If the edge length is aa, then the length, breadth, and height are all equal to aa.

The volume of any right prism (like a cuboid) is calculated as the Area of the Base multiplied by the Height. For a cuboid, the base is a rectangle (Area=l×bArea = l \times b), so the Volume becomes Area×h=l×b×hArea \times h = l \times b \times h.

Capacity is a term used for the volume of a substance (liquid or gas) that a hollow container can hold. While volume usually refers to the space occupied by the solid material itself, capacity refers to the internal space available for storage.

Units of volume are derived from linear units and are expressed as cubic units. Common units include cm3cm^3 (cubic centimeters), m3m^3 (cubic meters), and mm3mm^3. For liquids, we use Litres (LL) and Millilitres (mLmL).

Conversion between units is crucial: 11 cubic meter (m3m^3) is equal to 1,000,000cm31,000,000 cm^3. In terms of liquid capacity, 1000cm3=1L1000 cm^3 = 1 L and 1m3=1000L1 m^3 = 1000 L. This means 1cm31 cm^3 is equivalent to 1mL1 mL.

📐Formulae

Volume of a Cuboid=l×b×h\text{Volume of a Cuboid} = l \times b \times h

Volume of a Cube=a3\text{Volume of a Cube} = a^3

Area of Base of Cuboid=l×b\text{Area of Base of Cuboid} = l \times b

Capacity in Litres (from cm3)=Volume in cm31000\text{Capacity in Litres (from } cm^3) = \frac{\text{Volume in } cm^3}{1000}

Capacity in Litres (from m3)=Volume in m3×1000\text{Capacity in Litres (from } m^3) = \text{Volume in } m^3 \times 1000

💡Examples

Problem 1:

A matchbox measures 4cm×2.5cm×1.5cm4 cm \times 2.5 cm \times 1.5 cm. What will be the volume of a packet containing 1212 such boxes?

Solution:

Step 1: Identify the dimensions of one matchbox. Length l=4cml = 4 cm, Breadth b=2.5cmb = 2.5 cm, Height h=1.5cmh = 1.5 cm. Step 2: Calculate the volume of one matchbox using the formula V=l×b×hV = l \times b \times h. V=4×2.5×1.5=15cm3V = 4 \times 2.5 \times 1.5 = 15 cm^3. Step 3: Calculate the volume of 1212 such boxes. Total Volume =12×15=180cm3= 12 \times 15 = 180 cm^3.

Explanation:

We first find the space occupied by a single cuboidal unit and then multiply it by the total quantity to find the collective volume.

Problem 2:

A cubical water tank is 6m6 m long, 5m5 m wide and 4.5m4.5 m deep. How many litres of water can it hold? (Given 1m3=1000L1 m^3 = 1000 L)

Solution:

Step 1: Identify the dimensions of the tank. Length l=6ml = 6 m, Breadth b=5mb = 5 m, Depth (Height) h=4.5mh = 4.5 m. Step 2: Calculate the volume of the tank in cubic meters. V=l×b×h=6×5×4.5=135m3V = l \times b \times h = 6 \times 5 \times 4.5 = 135 m^3. Step 3: Convert the volume from cubic meters to litres. Capacity in litres =135×1000=135,000L= 135 \times 1000 = 135,000 L.

Explanation:

The volume is first calculated in standard units (m3m^3) based on the tank's dimensions, and then converted to capacity in litres using the standard conversion factor.