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

A cube has a total of 14 edges.

FAQ

Everything you need to know about this question

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

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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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