Question

The four angles of a quadrilateral form an A.P.If the sum of first three angle is twice the fourth angle.Find the angles

Answer 1

let the angles be a-3d, a-d, a+d, a+3d,in order.

sum of all the angles is 360°

so, 4a = 360
a= 90

also, a-3d+a-d+a+d =2(a + 3d)
3a-3d = 2a+ 6d
a= 9d

90= 9d
d = 10

hence the angles are 60, 80, 100, 120