Learn with Amar
Teaching video
A teaching recording for this chapter has not been published yet. Start with the worked example below and explore the related animations where available.
Grade 6 chapters and video availability01 · Read and understand
What you will learn
- Sum the six rectangular faces of a rectangular prism.
- Explain your method and check what the result means in the stated situation.
Before you start
Fraction and decimal operations, whole-number factors, measurement units, and reading simple tables.
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 closed box is 5 cm by 3 cm by 2 cm. What is its surface area?
Why this math matters
Use a labeled net to plan the ideal material area needed to cover a box. 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.
Count every face in surface area
PausedQuestion: Start with the question. Paused.
Question
Start with the question
An ideal closed box is 5 cm by 3 cm by 2 cm. What is its surface area?
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
Face areas: 5×3=15, 5×2=10, 3×2=6 cm²
There are three different face dimensions.
Connect the parts
Each type occurs twice
Opposite faces of the rectangular box match.
State and check the result
Surface area = 2(15 + 10 + 6) = 62 cm²
This measures the outside covering, not the interior volume.
The result
Surface area = 2(15 + 10 + 6) = 62 cm²
This measures the outside covering, not the interior volume.
Common mistakes to catch
- Count each face once.
- Open containers have fewer covering faces than closed boxes.
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
Find surface area of a cube with side 4 cm.
Show a hint
Six equal square faces each have area sixteen.
Reveal answer and explanation
96 cm²
6 × 4² = 96.
Practice 2
If the 5 by 3 top is removed from the main box, what face area remains?
Show a hint
Subtract that one missing face.
Reveal answer and explanation
47 cm²
62 − 15 = 47; this ignores material thickness and seams.
Take the idea with you
Use a labeled net to plan the ideal material area needed to cover a box.
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: Use fractional edges in a volume model
Completion is your own study record, not a test score. It stays in this browser, does not sync to another device, and can be removed by clearing browser data.