Learn with Amar
Teaching video
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Grade 2 chapters and video availability01 · Read and understand
What you will learn
- Add boundary side lengths to find a polygon's perimeter.
- Explain your method and check what the result means in the stated situation.
Before you start
Counting and comparing whole numbers, basic addition and subtraction, and recognizing simple shapes.
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
A rectangle has sides 6 cm, 3 cm, 6 cm, and 3 cm. How far is it around the boundary?
Why this math matters
Find the length of trim needed to go once around a simple paper shape. 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.
Measure all the way around
PausedQuestion: Start with the question. Paused.
Question
Start with the question
A rectangle has sides 6 cm, 3 cm, 6 cm, and 3 cm. How far is it around the boundary?
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
Trace all four sides
Perimeter follows the complete outside edge.
Connect the parts
6 + 3 + 6 + 3
Include each side exactly once.
State and check the result
Perimeter = 18 cm
The result is a length, not the number of squares inside.
The result
Perimeter = 18 cm
The result is a length, not the number of squares inside.
Common mistakes to catch
- Do not count only length plus width.
- The inside area and the outside boundary answer different questions.
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 triangle has sides 4 cm, 5 cm, and 6 cm. Find its perimeter.
Show a hint
Add all three sides.
Reveal answer and explanation
15 cm
4 + 5 + 6 = 15.
Practice 2
A square has four 7 cm sides. Is its perimeter 14 cm?
Show a hint
Four sides must be counted.
Reveal answer and explanation
No; 28 cm
7 + 7 + 7 + 7 = 28 cm.
Take the idea with you
Find the length of trim needed to go once around a simple paper shape.
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: Cover a rectangle without gaps
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