Difference between revisions of "2014 AMC 8 Problems/Problem 15"
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<math> \textbf{(A) }75\qquad\textbf{(B) }80\qquad\textbf{(C) }90\qquad\textbf{(D) }120\qquad\textbf{(E) }150 </math> | <math> \textbf{(A) }75\qquad\textbf{(B) }80\qquad\textbf{(C) }90\qquad\textbf{(D) }120\qquad\textbf{(E) }150 </math> | ||
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+ | ==Video Solution (CREATIVE THINKING)== | ||
+ | https://youtu.be/3QHH9xV-QDw | ||
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+ | ~Education, the Study of Everything | ||
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==Video Solution== | ==Video Solution== | ||
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https://youtu.be/aZhjhb3mMfg ~savannahsolver | https://youtu.be/aZhjhb3mMfg ~savannahsolver | ||
− | ==Video Solution | + | ==Video Solution == |
https://youtu.be/abSgjn4Qs34?t=3242 | https://youtu.be/abSgjn4Qs34?t=3242 | ||
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==Solution== | ==Solution== | ||
− | For this problem, it is useful to know that the measure of an inscribed angle is half the measure of its corresponding central angle. Since each unit arc is <math>\frac{1}{12}</math> of the circle's circumference, each unit central angle measures <math>\left( \frac{360}{12} \right) ^{\circ}=30^{\circ}</math>. Then, we know that the central angle of x = <math>60</math>, so inscribed angle = <math>30</math>. Also, central angle of y = <math>120</math>, so | + | For this problem, it is useful to know that the measure of an inscribed angle is half the measure of its corresponding central angle. Since each unit arc is <math>\frac{1}{12}</math> of the circle's circumference, each unit central angle measures <math>\left( \frac{360}{12} \right) ^{\circ}=30^{\circ}</math>. Then, we know that the central angle of x = <math>60</math>, so inscribed angle = <math>30</math>. Also, central angle of y = <math>120</math>, so inscribed angle = <math>60</math>. Summing both inscribed angles gives <math>30 + 60 = \boxed{(C)\ 90}.</math> |
==See Also== | ==See Also== | ||
{{AMC8 box|year=2014|num-b=14|num-a=16}} | {{AMC8 box|year=2014|num-b=14|num-a=16}} | ||
{{MAA Notice}} | {{MAA Notice}} |
Latest revision as of 18:06, 17 June 2024
Contents
Problem
The circumference of the circle with center is divided into equal arcs, marked the letters through as seen below. What is the number of degrees in the sum of the angles and ?
Video Solution (CREATIVE THINKING)
~Education, the Study of Everything
Video Solution
https://www.youtube.com/watch?v=qseG63LK4AU ~David
https://youtu.be/aZhjhb3mMfg ~savannahsolver
Video Solution
https://youtu.be/abSgjn4Qs34?t=3242
Solution
For this problem, it is useful to know that the measure of an inscribed angle is half the measure of its corresponding central angle. Since each unit arc is of the circle's circumference, each unit central angle measures . Then, we know that the central angle of x = , so inscribed angle = . Also, central angle of y = , so inscribed angle = . Summing both inscribed angles gives
See Also
2014 AMC 8 (Problems • Answer Key • Resources) | ||
Preceded by Problem 14 |
Followed by Problem 16 | |
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 |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.