document.write( "Question 452082: The sum of the measures of three of the interior angles of a pentagon is 280. The measure of the fourth angle is three times the measure of the fifth. Find the measure of the fourth angle? \n" ); document.write( "

Algebra.Com's Answer #310759 by pedjajov(51) $\"\"$ $\"About$

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The sum of the angles in pentagon is 540.
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\n" ); document.write( "So if fourth angle is x and fifth is y we have
\n" ); document.write( "280+x+y=540
\n" ); document.write( "x=3y -> y=x/3
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\n" ); document.write( "Substitute y into first equation
\n" ); document.write( "280+x+x/3=540, multiply by 3
\n" ); document.write( "840+3x+x=1620, subtract 840 from both sides, combine x
\n" ); document.write( "4x=780, divide by 4 both sides
\n" ); document.write( "x=195, this is measure of the fourth angle
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\n" ); document.write( "check:
\n" ); document.write( "280+195+195/3 = 540, ok
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