Q. The ratio of the angles ∠A and ∠B of a non-square rhombus ABCD is 4 : 5, the value of ∠C will be
a) 50°
b) 95°
c) 45°
d) 80°
Correct Answer: d) 80°
Question from UPPSC Prelims CSAT 2025
Explanation:
In a rhombus (a parallelogram), adjacent angles are supplementary and opposite angles are equal.
Let ∠A = 4x and ∠B = 5x. Then 4x + 5x = 180°, so x = 20°. Hence ∠A = 80° and ∠B = 100°. Since ∠C is opposite ∠A, ∠C = ∠A = 80°.
The ‘non-square’ condition just ensures the angles aren’t 90° and doesn’t affect the calculation.