The underwater aquarium volume quest

Quick answer

You can find the volume of an underwater aquarium by measuring its length, width, and depth, then multiplying these three numbers together. Volume tells you how much space is inside the tank, which helps you know how much water it can hold.

Learning outcome

By the end of this page, you will be able to measure the volume of a rectangular aquarium in litres by multiplying its length, width, and depth.

• You can identify the length, width, and depth of a tank.
• You can multiply three numbers to find volume.
• You can convert cubic centimetres to litres.
• You can use volume to work out how much water a tank holds.

Why this matters

Understanding volume helps you solve real-world problems, like how much water is needed to fill a fish tank, how much space a new aquarium will take up, or how many fish can safely live in a tank. It's useful for planning, saving water, and making sure your pets have enough room to swim and stay healthy.

In games and real life, you might need to find volume when building, cooking, or even planning a party. Volume is part of how we measure and understand space around us.

How it works

Volume is how much space something takes up. For a rectangular tank, you can find volume by multiplying:

1. Length (how long the tank is)
2. Width (how wide the tank is)
3. Depth (how deep the water goes)

The result is in cubic units (like cubic centimetres or cubic metres). To convert to litres, remember that 1 cubic centimetre = 1 millilitre, and 1000 millilitres = 1 litre.

Examples you can see

Imagine you have a rectangular aquarium that is:

• 50 cm long
• 30 cm wide
• 40 cm deep

First, multiply the three numbers:

50 × 30 × 40 = 60,000 cubic centimetres

Now convert to litres:

60,000 cubic centimetres ÷ 1000 = 60 litres

So, this tank holds 60 litres of water.

Real-world example: A child is helping to set up a new aquarium for a pet fish. They know the tank is 60 cm long, 40 cm wide, and 50 cm deep. How many litres of water will it hold?

60 × 40 × 50 = 120,000 cubic centimetres

120,000 ÷ 1000 = 120 litres

The aquarium will hold 120 litres of water.

Try it as a mini adventure

The Underwater Aquarium Volume Quest

You are a marine biologist helping to build a new aquarium for a local zoo. You need to find how much water each tank will hold. Here’s your mission:

1st time: Measure a tank that is 40 cm long, 25 cm wide, and 30 cm deep.

2nd time: Multiply the measurements to find cubic centimetres.

3rd time: Convert to litres.

4th time: Write your answer.

Challenge: If you have two tanks with the same dimensions, how many litres of water do they hold together?

Answer:

1st time: 40 × 25 × 30 = 30,000 cubic centimetres

2nd time: 30,000 ÷ 1000 = 30 litres

3rd time: Two tanks = 30 × 2 = 60 litres

Common mistakes

• Mistake: Forgetting to convert cubic centimetres to litres.
• Why it happens: Kids may not remember that 1000 ml = 1 litre.
• Fix: Always divide by 1000 to convert to litres.
• Mistake: Mixing up length, width, and depth.
• Why it happens: It's easy to get confused when measuring different sides.
• Fix: Label your measurements clearly or draw a quick sketch of the tank.
• Mistake: Not using the correct units in the final answer.
• Why it happens: Kids might write "60" instead of "60 litres".
• Fix: Always add the unit (litres) to your final answer.

Parent and carer guide

Help your child by:

1. Encouraging them to measure real aquariums or boxes at home.
2. Using a ruler or measuring tape to check their work.
3. Reinforcing that volume = length × width × depth.
4. Practising conversions (cubic cm to litres) with simple numbers.
5. Letting them explain their thinking aloud – this helps them learn!

Don’t worry if they make a mistake – it’s part of learning. Celebrate their effort and help them fix it with a gentle "Let’s try that again".

Practice questions

1. Find the volume of a tank that is 30 cm long, 20 cm wide, and 25 cm deep.
2. A tank is 50 cm long, 30 cm wide, and 40 cm deep. How many litres does it hold?
3. If a tank holds 100 litres, and it is 50 cm long and 20 cm wide, how deep is it?
4. Two tanks are each 40 cm long, 30 cm wide, and 25 cm deep. How many litres do they hold together?
5. How many litres of water will a tank hold if it is 60 cm long, 40 cm wide, and 50 cm deep?

Answers:

1. 30 × 20 × 25 = 15,000 cubic cm = 15 litres
2. 50 × 30 × 40 = 60,000 cubic cm = 60 litres
3. 100 litres = 100,000 cubic cm. 100,000 ÷ (50 × 20) = 100,000 ÷ 1000 = 100 cm deep
4. 40 × 30 × 25 = 30,000 cubic cm = 30 litres each. 30 × 2 = 60 litres
5. 60 × 40 × 50 = 120,000 cubic cm = 120 litres

FAQ

What is volume?

Volume is how much space something takes up. For a tank, it tells you how much water it can hold.

How do I know which side is length, width, and depth?

Length is usually the longest side, width is the shorter side, and depth is how deep the tank goes. You can measure each side and label them.

Why do I need to convert to litres?

It’s easier to understand how much water is in a tank when we use litres instead of cubic centimetres.

Can I use this for any shape of tank?

This method works for rectangular tanks. For other shapes like round tanks, the maths is a bit different.

How can I practice volume at home?

Use boxes, containers, or even your bath to measure and calculate volume. Try to convert your results to litres!