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
- Use a perpendicular height in the triangle area formula.
- 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
A triangle has base 10 cm and perpendicular height 6 cm. What area?
Why this math matters
Relate unfamiliar triangular regions to rectangles or parallelograms with the same base and height. 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.
Find triangle area from a rectangle
PausedQuestion: Start with the question. Paused.
Question
Start with the question
A triangle has base 10 cm and perpendicular height 6 cm. What 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
Matching rectangle area = 10 × 6 = 60 cm²
The rectangle shares the base and perpendicular height.
Connect the parts
Triangle is half of the corresponding parallelogram
A congruent second triangle completes that double-area shape.
State and check the result
A = 1/2 × 10 × 6 = 30 cm²
The sloping side length is not the height unless it is perpendicular to the base.
The result
A = 1/2 × 10 × 6 = 30 cm²
The sloping side length is not the height unless it is perpendicular to the base.
Common mistakes to catch
- Use a perpendicular height, not any sloping edge.
- Remember the factor one half.
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 area 24 m² and base 8 m. Find its height.
Show a hint
Solve 24 = (1/2) × 8 × h.
Reveal answer and explanation
6 m
The doubled area is forty-eight, and 48/8 = 6.
Practice 2
Can a triangle's height lie outside an obtuse triangle?
Show a hint
Extend the base line to draw a perpendicular.
Reveal answer and explanation
Yes
Height is the perpendicular distance to the base's supporting line.
Take the idea with you
Relate unfamiliar triangular regions to rectangles or parallelograms with the same base and height.
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: Slide a triangle to measure a parallelogram
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