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CEMC Gauss (Grade 8), 2012

Algebra Difficulty 1.2 Junior Find the answer Canada

How many more coins does it take to make one dollar (100) using only nickels(5 coins) than it takes to make one dollar using only dimes (10 coins)?

Pick one

Solution

Solution 1

The angle marked $\Box$ is vertically opposite the angle measuring $60\degree$ .

Since vertically opposite angles are equal, then the measure of the angle marked $\Box$ is also $60\degree$ .

Solution 2

The measure of a straight angle is $180\degree$ .

Together, the angle measuring $120\degree$ and the angle marked $\Box$ make up a straight angle.

That is, $120\degree + \Box = 180\degree$ .
Therefore, the angle marked $\Box$ is $60\degree$ .

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