Find X in a Cuboid: Volume 60 cm³ with Dimension (X+2)

Cuboid Volume Equations with Algebraic Dimensions

Look at the cuboid of the figure:

The volume of the cuboid is

60 cm³.

Work out the value of X.

333AAABBBDDDCCCEEEGGGFFFHHH5X+2

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:03 Use the formula for calculating box volume
00:06 height times length times width
00:12 Substitute appropriate values and solve for X
00:34 Isolate X
00:47 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

Look at the cuboid of the figure:

The volume of the cuboid is

60 cm³.

Work out the value of X.

333AAABBBDDDCCCEEEGGGFFFHHH5X+2

2

Step-by-step solution

To solve the problem of finding X X for a cuboid with a given volume, we proceed as follows:

  • Step 1: Identify the dimensions of the cuboid: 5cm 5 \, \text{cm} , X+2cm X+2 \, \text{cm} , and 3cm 3 \, \text{cm} .
  • Step 2: Recall the volume formula for a cuboid: V=l×w×h V = l \times w \times h .
  • Step 3: Substitute the known values into the volume equation: 5×(X+2)×3=60 5 \times (X+2) \times 3 = 60 .

Now, let's solve this equation step-by-step:

First, calculate the product involving X X :
5×3×(X+2)=60 5 \times 3 \times (X + 2) = 60 .

Simplify the left side:
15×(X+2)=60 15 \times (X + 2) = 60 .

Next, distribute the 15 on the left side:
15X+30=60 15X + 30 = 60 .

To isolate X X , subtract 30 from both sides:
15X=30 15X = 30 .

Finally, divide both sides by 15 to solve for X X :
X=2 X = 2 .

Therefore, the value of X X is 2 2 .

3

Final Answer

2 2

Key Points to Remember

Essential concepts to master this topic
  • Volume Formula: For cuboids multiply length × width × height
  • Technique: Substitute 5 × (X+2) × 3 = 60, then simplify to 15(X+2) = 60
  • Check: When X = 2, volume is 5 × 4 × 3 = 60 cm³ ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to distribute multiplication through algebraic expressions
    Don't write 15 × (X+2) = 15X + 2 instead of 15X + 30 = wrong answer! This ignores the distributive property and gives incorrect solutions. Always multiply the coefficient by every term inside parentheses.

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

How do I know which dimensions to multiply?

+

For any cuboid, multiply all three dimensions together: length × width × height. The order doesn't matter - just make sure you use all three measurements!

What if I can't see all the dimensions clearly?

+

Look carefully at the diagram labels. In this problem, the dimensions are 5 (bottom edge), X+2 (side edge), and 3 (height). Each cuboid has exactly three different measurements.

Why do I need to solve for X instead of just calculating volume?

+

The volume is already given as 60 cm³! Your job is to work backwards - use the known volume and two known dimensions to find the unknown dimension X+2.

Can X be negative in this problem?

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No! Since X+2 represents a length, it must be positive. If your algebra gives you X = -5, that would mean a dimension of -3 cm, which is impossible for a real object.

How do I check my answer is reasonable?

+

Substitute back: if X = 2, then dimensions are 5 × 4 × 3. Calculate: 5 × 4 × 3 = 60 ✓ This matches the given volume, so X = 2 is correct!

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