One side of a triangle is produced and the exterior angle so formed is 140°. If the corresponding interior opposite angles are in the ratio 3:4, find the measure of all the angles of the triangle.
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Solution
Weknow that, Exterior angle = sum of opposite interior angles
given that ratio of interior angle = 3:4
required angles are 3x and 4x
that is 3x+4x = 140 according to given condition
solving this will gives
7x= 140
x =140/7
x= 20
therefore the angles are 3*20 and 4*20
that is 60 degree and 80 degree
now we want to find the third angle .
we know that the sum of the interior angles of a triangle = 180