Difference between revisions of "1999 CEMC Gauss (Grade 7) Problems/Problem 6"

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==Problem==
 
==Problem==
 
In <math>\Delta ABC</math>, <math>\angle B = 72^{\circ}</math>. What is the sum, in degrees, of the other two angles?
 
In <math>\Delta ABC</math>, <math>\angle B = 72^{\circ}</math>. What is the sum, in degrees, of the other two angles?
 
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<math>\text{(A)}\ 144 \qquad \text{(B)}\ 72 \qquad \text{(C)}\ 108 \qquad \text{(D)}\ 110 \qquad \text{(E)}\ 288 </math>
 
<math>\text{(A)}\ 144 \qquad \text{(B)}\ 72 \qquad \text{(C)}\ 108 \qquad \text{(D)}\ 110 \qquad \text{(E)}\ 288 </math>
 
==Solution==
 
==Solution==

Latest revision as of 12:31, 22 April 2025

Problem

In $\Delta ABC$, $\angle B = 72^{\circ}$. What is the sum, in degrees, of the other two angles?


An image is supposed to go here. You can help us out by creating one and editing it in. Thanks.


$\text{(A)}\ 144 \qquad \text{(B)}\ 72 \qquad \text{(C)}\ 108 \qquad \text{(D)}\ 110 \qquad \text{(E)}\ 288$

Solution

Let x and y be the other two angles of the triangle.

The sum of the interior angles in a triangle is always $180^{\circ}$, so we have:

$x + y + 72^{\circ} = 180^{\circ}$

Subtracting $72^{\circ}$ from both sides of the equation gives:

$x + y = \boxed{\textbf{(C)} 108}$