Difference between revisions of "2017 AMC 8 Problems/Problem 6"

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~MathFun1000
 
~MathFun1000
  
==Solution 3 (Brute Force) NOT RECOMMENDED==
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==Solution 4 (Brute Force) NOT RECOMMENDED==
  
 
Since we see the ratio is <math>3:3:4</math>, we can rule out the answer of <math>{\textbf{(E) }90}</math> because the numbers in the ratio are too big to have <math>90^\circ</math>. Also, we are trying to find the largest angle and all the other angles except for 72 are too small to be the largest angle. Using all this, our answer is <math>\boxed{\textbf{(D) }72}</math>.
 
Since we see the ratio is <math>3:3:4</math>, we can rule out the answer of <math>{\textbf{(E) }90}</math> because the numbers in the ratio are too big to have <math>90^\circ</math>. Also, we are trying to find the largest angle and all the other angles except for 72 are too small to be the largest angle. Using all this, our answer is <math>\boxed{\textbf{(D) }72}</math>.

Revision as of 10:23, 17 February 2023

Problem

If the degree measures of the angles of a triangle are in the ratio $3:3:4$, what is the degree measure of the largest angle of the triangle?

$\textbf{(A) }18\qquad\textbf{(B) }36\qquad\textbf{(C) }60\qquad\textbf{(D) }72\qquad\textbf{(E) }90$

Solution 1

The sum of the ratios is $10$. Since the sum of the angles of a triangle is $180^{\circ}$, the ratio can be scaled up to $54:54:72$ $(3\cdot 18:3\cdot 18:4\cdot 18).$ The numbers in the ratio $54:54:72$ represent the angles of the triangle. The question asks for the largest, so the answer is $\boxed{\textbf{(D) }72}$.

Solution 2

We can denote the angles of the triangle as $3x$, $3x$, $4x$. Due to the sum of the angles in a triangle, $3x+3x+4x=180^{\circ}\implies x=18^{\circ}$. The greatest angle is $4x$ and after substitution we get $\boxed{\textbf{(D) }72}$.

~MathFun1000

Solution 4 (Brute Force) NOT RECOMMENDED

Since we see the ratio is $3:3:4$, we can rule out the answer of ${\textbf{(E) }90}$ because the numbers in the ratio are too big to have $90^\circ$. Also, we are trying to find the largest angle and all the other angles except for 72 are too small to be the largest angle. Using all this, our answer is $\boxed{\textbf{(D) }72}$.

~jason.ca

Video Solution

https://youtu.be/rQUwNC0gqdg?t=635

https://youtu.be/ykR1ApGP0Qg

~savannahsolver

See Also

2017 AMC 8 (ProblemsAnswer KeyResources)
Preceded by
Problem 5
Followed by
Problem 7
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
All AJHSME/AMC 8 Problems and Solutions

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