SOLUTION: find the measure of two supplementary angles such that one angle is four fifths as large as the other

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Question 1137545: find the measure of two supplementary angles such that one angle is four fifths as large as the other
Answer by MathLover1(20850) About Me  (Show Source):
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supplementary angles are two angles whose sum is 180°
let one angle be alpha and its supplement beta
alpha%2Bbeta=180°
if one angle is four fifths as large as the other, we have beta=%284%2F5%29alpha
substitute it in alpha%2Bbeta=180°
alpha%2B%284%2F5%29alpha=180°......both sides multiply by 5
5alpha%2B4alpha=180%2A5°
9alpha=900°
alpha=100°
then beta=%284%2F5%29100°=>beta=80°