Calculate Cuboid Length: Volume 96 cm³ with 3:2 Ratio and Height 4 cm

Volume Formulas with Length-Width Ratios

A cuboid has a height of 4 cm.

The ratio between its length and its width is 3:2.

The volume of the cuboid is equal to 96 cm³.

Calculate the length of the cuboid.

444

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:13 Let's find the length of the box.
00:16 Here's the ratio of the edges based on the data given.
00:23 We'll call the unknown value X.
00:30 Let's use the formula to calculate the box's volume.
00:35 That's width times height times length.
00:38 Now, put the right values in the formula and solve for X.
01:04 We need to get X by itself.
01:18 This gives us X. It must be positive since it's an edge length.
01:23 Use the X value to determine the box's length.
01:33 And there you go! That's the solution.

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

A cuboid has a height of 4 cm.

The ratio between its length and its width is 3:2.

The volume of the cuboid is equal to 96 cm³.

Calculate the length of the cuboid.

444

2

Step-by-step solution

To solve this problem, we need to find the length of the cuboid using its volume and given dimensions. Let's break this down:

  • Step 1: Express the length and width using the ratio given. Let l=3x l = 3x and w=2x w = 2x , where x x is a common factor.
  • Step 2: Apply the formula for the volume of the cuboid, V=l×w×h V = l \times w \times h . Given that h=4 h = 4 cm and V=96 V = 96 cm³, the equation becomes:
96=(3x)×(2x)×4 96 = (3x) \times (2x) \times 4

Now, simplify and solve for x x :

96=24x2 96 = 24x^2

Dividing both sides by 24 gives:

x2=4 x^2 = 4

Taking the square root of both sides, we find:

x=2 x = 2

Thus, the length of the cuboid is:

l=3x=3×2=6 cm l = 3x = 3 \times 2 = 6 \text{ cm}

Therefore, the solution to the problem is 6 cm 6 \text{ cm} .

3

Final Answer

6 cm

Key Points to Remember

Essential concepts to master this topic
  • Volume Formula: For cuboids, V = length × width × height
  • Ratio Method: Let length = 3x and width = 2x when ratio is 3:2
  • Check: Verify 6 × 4 × 4 = 96 cm³ matches given volume ✓

Common Mistakes

Avoid these frequent errors
  • Using the ratio directly as actual measurements
    Don't assume length = 3 cm and width = 2 cm just from 3:2 ratio = volume of only 24 cm³! The ratio shows proportions, not actual sizes. Always use variables like 3x and 2x, then solve for x using the volume formula.

Practice Quiz

Test your knowledge with interactive questions

A rectangular prism has a base measuring 5 units by 8 units.

The height of the prism is 12 units.

Calculate its volume.

121212888555

FAQ

Everything you need to know about this question

Why can't I just use 3 and 2 as the length and width?

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The ratio 3:2 tells us the proportion, not the actual measurements! If length was 3 cm and width was 2 cm, the volume would be 3×2×4=24 3 \times 2 \times 4 = 24 cm³, not 96 cm³.

How do I set up the variables from the ratio?

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When the ratio is 3:2, let length = 3x and width = 2x. The variable x is a scale factor that makes the measurements fit the actual volume.

What if I get a negative value for x?

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Since we're dealing with lengths, x must be positive. If you get a negative square root, double-check your equation setup and calculations.

Can I solve this without using variables?

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Using variables with ratios is the most reliable method. Guessing and checking might work, but it's time-consuming and you might miss the correct answer.

How do I know which dimension is length vs width?

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In this problem, it doesn't matter! Since we multiply length × width, getting 6 cm and 4 cm gives the same volume whether 6 is length or width.

What's the fastest way to check my answer?

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Substitute back: 6×4×4=96 6 \times 4 \times 4 = 96 cm³. Also verify the ratio: 6:4=3:2 6:4 = 3:2

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