Calculate Rectangular Prism Volume Using Areas of 15 cm² and 24 cm²

Volume Calculation with Given Face Areas

Look at the rectangular prism below.

The area of rectangle CAEG is 15 cm².

The area of rectangle ABFE is 24 cm².

Calculate the volume of the rectangular prism ABCDEFGH.

AAABBBDDDCCCEEEGGGFFFHHH3

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the volume of box ABCDEFGH
00:03 Data values
00:10 Mark side GE with letter X
00:13 Use the formula to calculate rectangle area length times width
00:16 Insert appropriate values and solve for X
00:20 This is the length GE
00:23 Now use the same method to find EF
00:29 Mark EF with letter Y
00:33 Insert into formula for rectangle area and solve for Y
00:38 This is the width EF
00:41 Calculate volume using length(8) times width(5) times height(3)
00:44 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 rectangular prism below.

The area of rectangle CAEG is 15 cm².

The area of rectangle ABFE is 24 cm².

Calculate the volume of the rectangular prism ABCDEFGH.

AAABBBDDDCCCEEEGGGFFFHHH3

2

Step-by-step solution

Since we are given the area of rectangle CAEG and length AE, we can find GE:

Let's denote GE as X and substitute the data in the rectangle area formula:

3×x=15 3\times x=15

Let's divide both sides by 3:

x=5 x=5

Therefore GE equals 5

Since we are given the area of rectangle ABFE and length AE, we can find EF:

Let's denote EF as Y and substitute the data in the rectangle area formula:

3×y=24 3\times y=24

Let's divide both sides by 3:

y=8 y=8

Therefore EF equals 8

Now we can calculate the volume of the box:

3×5×8=15×8=120 3\times5\times8=15\times8=120

3

Final Answer

120 120

Key Points to Remember

Essential concepts to master this topic
  • Rectangular Prism Dimensions: Use given face areas and shared edges to find all three dimensions
  • Finding Unknown Dimensions: From Area = length × width, solve 15=3×x 15 = 3 \times x to get x = 5
  • Volume Verification: Check that 3×5×8=120 3 \times 5 \times 8 = 120 cm³ using all three dimensions ✓

Common Mistakes

Avoid these frequent errors
  • Using area values directly as volume without finding dimensions
    Don't multiply the given areas (15 × 24 = 360) thinking this gives volume! This ignores the rectangular prism structure and shared edges. Always find the three individual dimensions first using Area = length × width, then multiply length × width × height for volume.

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 edge belongs to which rectangle?

+

Look at the vertex labels carefully! Rectangle CAEG shares edge AE with rectangle ABFE. The edge AE = 3 is common to both rectangles, so use it to find the other dimensions.

Why can't I just multiply the two given areas together?

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Areas are 2-dimensional measurements, not the 3D dimensions you need for volume! You must use Area = length × width to find each missing dimension first.

What if I can't see the 3D shape clearly in the diagram?

+

Focus on the rectangle names instead! CAEG and ABFE tell you exactly which vertices form each rectangle. The shared letters (A and E) show the common edge.

How do I check if my volume answer is reasonable?

+

Compare your dimensions: 3 cm × 5 cm × 8 cm. The volume 120 cm³ should be larger than any single face area (15 cm² or 24 cm²), which makes sense!

What if I get the dimensions mixed up?

+

It doesn't matter which dimension you call length, width, or height! As long as you multiply all three dimensions together, you'll get the correct volume of 120 cm³.

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