Learn with Amar
Teaching video
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Grade 5 chapters and video availability01 · Read and understand
What you will learn
- Multiply length, width, and height for a rectangular prism.
- Explain your method and check what the result means in the stated situation.
Before you start
Multi-digit operations, equivalent fractions, decimal place value, and rectangular area.
Keep paper nearby. Read the question once for the context, then again to identify what is known and what you need to find.
Start with a question
An ideal rectangular box is 6 cm long, 4 cm wide, and 3 cm high inside. Find its internal volume.
Why this math matters
Estimate the capacity of an ideal rectangular container from its inner dimensions. The worked example shows how to connect the situation, its mathematical representation, and a check on the result.
Set up the model
A useful answer starts with clear assumptions:
- Use the units, grouping rules, and reference whole stated in the question.
- Treat the supplied counts and measurements as exact within the classroom model, unless an estimate or a random outcome is requested.
02 · Work through the example
Follow the reasoning, one step at a time.
Try to predict the next step before reading it. After each calculation, explain why the operation makes sense and how it helps answer the original question.
Work through it with Amar
See this example unfold.
The complete worked example, one idea at a time.
Derive the box-volume formula
PausedQuestion: Start with the question. Paused.
Question
Start with the question
An ideal rectangular box is 6 cm long, 4 cm wide, and 3 cm high inside. Find its internal volume.
Before you calculate
Read what is known and what you need to find. Make a prediction before moving to the first calculation.
Starts paused. Play advances through the full text at a reading pace; pause whenever you need more time. Previous, Next, and the phase buttons let you set your own pace. Playback pauses when this walkthrough leaves the screen or you switch tabs.
Your device’s reduced-motion setting keeps each phase still. Manual controls remain available. The full written solution stays below.
Represent the situation
Base area = 6 × 4 = 24 cm²
One centimetre-high layer contains twenty-four unit cubes.
Connect the parts
Height = 3 such layers
The prism has a constant rectangular cross-section.
State and check the result
Volume = 24 × 3 = 72 cm³
Equivalently, V = length × width × height.
The result
Volume = 24 × 3 = 72 cm³
Equivalently, V = length × width × height.
Common mistakes to catch
- Use internal dimensions for capacity.
- Base area times height works here because every layer has that same area.
03 · Practice independently
Try it before revealing the answer.
Use paper or a calculator as needed. Write your units and reasoning, then open the hint or explanation to check your approach.
Practice 1
A box is 5 m by 2 m by 4 m. Find volume.
Show a hint
Multiply the three perpendicular dimensions.
Reveal answer and explanation
40 m³
5 × 2 × 4 = 40.
Practice 2
A prism has base area 15 cm² and height 7 cm. Find volume.
Show a hint
Base area already combines two dimensions.
Reveal answer and explanation
105 cm³
15 × 7 = 105; no extra width factor is needed.
Take the idea with you
Estimate the capacity of an ideal rectangular container from its inner dimensions.
04 · Reflect and continue
Can you explain it in your own words?
Before moving on, explain the main idea without looking at the worked example. Try both practice questions, check your reasoning, and name one mistake you now know how to avoid. Return to a step if you still need support.
Up next: Add nonoverlapping solid volumes
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