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Problem 275

Geometry Difficulty 1.5 Multiple choice CEMC Gauss (Grade 7) · Canada · 2015

In the rectangle shown, the area of the shaded region is

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Official solution

The rectangle has area $5\times12=60$ cm $^2$ . Each of the two congruent unshaded triangles has area $\frac12\times2\times5=5$ cm $^2$ . The area of the shaded region is equal to the area of the rectangle minus the areas of the two unshaded triangles, which is $60-5-5=50$ cm $^2$ .

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