Carbon-11 has a half-life of about 20 minutes. If we start with 200 grams, how much will be left after 3 hours?
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The <em>missing</em> angle of the <em>right</em> triangle ABC has a measure of 30°. (Correct answer: A)
<h3>How to find a missing angle by triangle properties</h3>
Triangles are <em>geometrical</em> figures formed by three sides and whose sum of <em>internal</em> angles equals 180°. There are two kind of triangles existing in this question: (i) <em>Right</em> triangles, (ii) <em>Isosceles</em> triangles.
<em>Right</em> triangles are triangles which one of its angles equals 90° and <em>isosceles</em> triangles are triangles which two of its sides have <em>equal</em> measures.
According to the statement, we know that triangle BQR is an <em>isosceles</em> triangle, whereas triangles ABC, ANB and NBC are <em>right</em> triangles. Based on the figure attached below, we have the following system of <em>linear</em> equations based on <em>right</em> triangles ABC and NBC:
<em>2 · x + 90 + θ = 180</em> (1)
<em>(90 - x) + 90 + θ = 180</em> (2)
By equalizing (1) and (2) we solve the system for <em>x</em>:
<em>2 · x = 90 - x</em>
<em>3 · x = 90</em>
<em>x = 30</em>
And by (1) we solve the system for <em>θ</em>:
<em>θ = 180 - 2 · x - 90</em>
<em>θ = 30</em>
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The <em>missing</em> angle of the <em>right</em> triangle ABC has a measure of 30°. (Correct answer: A)
To learn more on right triangles, we kindly invite to check this verified question: brainly.com/question/6322314
