Question: A and B are complementary angles and m∠B = 30°. The measure of ∠A is _____________.

A ) 50°
B ) 60°
C ) 55°
D ) 70°

Steps to derive

1 Given, A and B are complementary angles.

2 m∠A + m∠B = 90°
 [Sum of the complementary angles is 90°.]

3 m∠A + 30° = 90°
 [Substitute m∠B = 30°.]

4 m∠A = 90° - 30°
 [Subtract 30° on both the sides.]

5 m∠A = 60°

6 So, m∠A = 60°.



Hence the right answer is Option B

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