Calculate Water Height: Finding Level in 125 cm³ Cube with 75 cm³ Water

Cube Volume Problems with Water Height

A cube has a volume equal to 125 cm3.

If we pour 75 cm³ of water into it, how high will the water reach?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 To what height will the water reach?
00:03 We'll use the formula for volume calculation (edge cubed)
00:07 We'll extract the cube root
00:12 This is the size of edge A
00:22 The height of the cube is the edge
00:27 We'll calculate the volume ratio
00:31 This is the volume ratio
00:34 The volume ratio equals the height ratio
00:38 We'll multiply the height by the ratio to find the water height
00:42 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

A cube has a volume equal to 125 cm3.

If we pour 75 cm³ of water into it, how high will the water reach?

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Calculate the side length of the cube.
  • Step 2: Find the base area of the cube.
  • Step 3: Determine the height the water reaches based on its volume.

Now, let's work through each step:

Step 1: The volume of the cube is 125cm3 125 \, \text{cm}^3 . Since the volume of a cube is given by s3 s^3 , we have:

s3=125 s^3 = 125

Taking the cube root of both sides gives:

s=1253=5cm s = \sqrt[3]{125} = 5 \, \text{cm}

Step 2: The base area of the cube is s2 s^2 , which is:

(5cm)2=25cm2 (5 \, \text{cm})^2 = 25 \, \text{cm}^2

Step 3: The volume of water is 75cm3 75 \, \text{cm}^3 , and we need to find the height h h it reaches in the cube:

75=25×h 75 = 25 \times h

Solving for h h :

h=7525=3cm h = \frac{75}{25} = 3 \, \text{cm}

Therefore, the height to which the water will reach is 3cm 3 \, \text{cm} .

3

Final Answer

3 3 cm

Key Points to Remember

Essential concepts to master this topic
  • Volume Formula: For cubes, volume equals side length cubed (s3 s^3 )
  • Technique: Find base area first: 52=25 cm2 5^2 = 25 \text{ cm}^2 then divide water volume
  • Check: Verify: 25×3=75 cm3 25 \times 3 = 75 \text{ cm}^3 matches water volume ✓

Common Mistakes

Avoid these frequent errors
  • Using total cube volume instead of base area
    Don't divide water volume by total cube volume (75 ÷ 125) = wrong height! This gives you a fraction of the cube, not actual height. Always find the base area first, then divide water volume by base area.

Practice Quiz

Test your knowledge with interactive questions

Identify the correct 2D pattern of the given cuboid:

444444999

FAQ

Everything you need to know about this question

Why can't I just divide 75 by 125 to get the height?

+

That would give you what fraction of the cube is filled, not the actual height! You need the base area (25 cm²) to find how high the water reaches.

What if the cube had a different volume?

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Same steps! Find the side length by taking the cube root, calculate base area by squaring the side, then divide water volume by base area.

How do I know the cube root of 125 is 5?

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Think: what number times itself three times equals 125? 5×5×5=125 5 \times 5 \times 5 = 125 . You can also use a calculator for cube roots!

Will the water always reach the same height in any container?

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No! The height depends on the container's base area. Same water volume in a wider container = lower height; narrower container = higher height.

What if I put more than 125 cm³ of water?

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The cube can only hold 125 cm³ maximum! Any extra water would overflow. Always check that water volume doesn't exceed cube volume.

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