RRB Group-D Model Paper 11 with answers for online practice

Consider triangle ABC such that ∠A + 2∠B = 180 ---(1) (given)
By Angle Sum Property,
We know that ∠A + ∠B + ∠C = 180
⇒ ∠A = 180 – (∠B + ∠C) ---(2)
From (1) and (2),
180 – 2∠B = 180 – (∠B + ∠C)
⇒ 2∠B = ∠B + ∠C
∴ ∠B = ∠C
∴ ΔABC is a isosceles triangle.