In parallelogram ABCD angle A and angle D are co interior angles and add up to 180 degrees. See details.?

Question

If angle A is four fifths the size of angle D, what is the size of the angles?

Answer 1

D + 4D/5 = 180 whence D = 100 degrees and A = 4*100/5 = 80 degrees.

Answer 2

a + d = 180

a = 4/5 d = .8d

1.8d = 180

d = 100 degrees

a = 80 degrees

Answer 3

Then a=(4/5)d and

a+d=180.

By subsituting, the

((4/5)d)+d=180 or

(9/5)d=180 so

d=(5*180)/9=100 and

a=180-100=80.

SO, d=100 and a=80.