Mon Prof Augmenté
Triangle and Rectangle
Age 12 · Maths
A rectangle can be split along a diagonal into two equal triangles. The area of one triangle is half the area of the rectangle.
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In the picture
- White triangular half: half the area of the rectangle.
- Blue triangular half: the other half of the rectangle’s area.
- Diagonal crease: the line that divides the rectangle into two equal halves.
- Bottom edge: the base of the rectangle and of each triangle.
Examples
- A rectangular slice of bread cut corner to corner into two triangular sandwiches.
- A rectangular garden bed divided by a diagonal path into two triangular flower beds.
Key takeaways
- A diagonal cuts a rectangle into two triangles of equal area.
- Triangle area is half the rectangle with the same base and height: base × height ÷ 2.
Quiz: Triangle and Rectangle (Age 12)
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A rectangle is divided by a diagonal into two triangles. What is true about their areas?
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How can you find the area of one triangle made by cutting a rectangle along a diagonal?
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A rectangle has an area of 24 square units. It is cut along a diagonal. What is the area of one triangle?
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