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 3 chapters and video availability01 · Read and understand
What you will learn
- Use length times width to count unit squares.
- Explain your method and check what the result means in the stated situation.
Before you start
Place value through hundreds, addition and subtraction, equal groups, and equal shares.
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 is 8 cm long and 3 cm wide. What is its area?
Why this math matters
Estimate covering material for a rectangular surface from two perpendicular measurements. 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 rectangle area from rows
PausedQuestion: Start with the question. Paused.
Question
Start with the question
A rectangle is 8 cm long and 3 cm wide. What is its 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
8 unit squares in each row
One-centimetre squares fit along the length.
Connect the parts
3 rows
The width sets the number of such rows.
State and check the result
8 × 3 = 24 cm²
Multiplying side counts gives the number of square-centimetre units.
The result
8 × 3 = 24 cm²
Multiplying side counts gives the number of square-centimetre units.
Common mistakes to catch
- Use square units for area.
- The length-times-width rule here assumes a rectangle.
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 the area of a 5 m by 7 m rectangle.
Show a hint
Multiply its two perpendicular lengths.
Reveal answer and explanation
35 m²
Five rows of seven square metres cover thirty-five square metres.
Practice 2
Why is 8 + 3 not the area?
Show a hint
Addition only combines lengths.
Reveal answer and explanation
It does not count rows of squares
Area requires the two-dimensional covering, given by multiplication here.
Take the idea with you
Estimate covering material for a rectangular surface from two perpendicular measurements.
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: Find area by joining rectangles
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