The ratio of the angles = 4: 7
∴ Let the angles be 4x and 7x.
Adding 10∘ to the smaller angle and subtracting 20∘ from the larger angle.
⇒Final values of
Smaller angle = 4x+10∘ and
Larger angle = 7x−20∘
The angles are now in the ratio 1 : 1
⇒4x+10∘=7x−20∘
⇒7x−4x=20∘+10∘
⇒3x=30∘
⇒x=10∘
∴ The value of smaller angle
=4x=40∘