Question

Two complementary angles are in the ratio 4:5. find the angle

Answer 1

let the angles be 4x and 5x
Complementary angle=sum of angles is 90'
4x+5x=90'
9x=90'
x=10
angles are4*10=40' and 5*10=50'

Answer 2

Sum of two complementary angles is 180 degree.
ratio = 4:5
Let the angles be - 4y and 5y

According To Question, Equation Formed Will Be-
Angle 1 + Angle 2 = 180 degree
4y + 5y = 180   
9y    =  180     
y    =  180/9     
 y    =  20 degree

therefore, Angle 1 = 4y = 4 x 20 = 80 degree             
                   Angle 2 = 5y = 5 x 20 = 100 degree