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CEMC Pascal, 2020

Combinatorics Difficulty 1.3 Junior Find the answer Canada

Matilda counted the birds that visited her bird feeder yesterday. She summarized the data in the bar graph shown.

The percentage of birds that were goldfinches is

$15\%$
$20\%$
$30\%$
$45\%$
$60\%$

Your answer

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Solutions — 2

Solution 1

From the bar graph, Matilda saw 6 goldfinches, 9 sparrows, and 5 grackles.

In total, she saw $6 + 9 + 5 = 20$ birds.

This means that the percentage of birds that were goldfinches is $\dfrac{6}{20} \times 100\% = \dfrac{3}{10} \times 100\% = 30\%$ .

Solution 2

From the bar graph, Matilda saw 6 goldfinches, 9 sparrows, and 5 grackles.

In total, she saw $6 + 9 + 5 = 20$ birds.

This means that the percentage of birds that were goldfinches is $\dfrac{6}{20} \times 100\% = \dfrac{3}{10} \times 100\% = 30\%$ .

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