Area of Triangle — Standard Formula
The area of a triangle is half the product of a chosen base and its corresponding height.
In one line: Triangle area is half of the matching rectangle or parallelogram.
Practice This ConceptUnderstand it
Any side of a triangle can be treated as base, but the height must be perpendicular to that base. The formula works for right, acute, and obtuse triangles when the correct height is used.
Formula and rule
Area = 1/2 × base × height.
The height must be perpendicular to the selected base.
See it worked out
Follow the example line by line, then use the same method on new questions.
Worked example
- 1A triangle has base 10 cm and height 8 cm.
- 2Area = 1/2 × 10 × 8 = 40 cm².
Method you can reuse
Visual tip
A triangle with base marked and perpendicular height drawn helps avoid using a slant side as height.
Check yourself
Answer the question in your head before opening the answer.
Try it yourself
A triangle has base 16 cm and perpendicular height 9 cm. What is its area?
Think first, then show answerHide answer
Common wrong answer
80 cm² for base 10 cm and height 8 cm.
Why it loses marks: The factor 1/2 is missed.
Don't mix this up
Exam tip
Write it in the exam
Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.
How CBSE asks it
- 1
Enough for 1 mark
The area of a triangle is half the product of a chosen base and its corresponding height.
- 2
Add for 2 marks
Example: If base = 12 cm and height = 5 cm, area = 1/2 × 12 × 5 = 30 cm².
- 3
Add for 3 marks
Any side of a triangle can be treated as base, but the height must be perpendicular to that base.
Practice this concept with focused MCQs
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