Problem 22 · 2011 Math Kangaroo
Stretch
Geometry & Measurement
area-decomposition
The picture shows a rectangle with four identical triangles. Determine the total area of the triangles.
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Answer: D — 56 cm²
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Hint 1 of 2
The four triangles are identical and pinwheel around the centre.
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Hint 2 of 2
Use the 30 cm and 14 cm measurements to find one triangle's area, then multiply by four.
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Approach: find one triangle's area from the given lengths
- The rectangle is 30 cm wide, split by a midline, with four identical right triangles pinwheeling about the centre.
- From the 30 cm and 14 cm measurements, each triangle has area 14 cm².
- Four identical triangles give 4 × 14 = 56 cm².
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