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Question

The measure of an angle is three times the measure of its complement. The angles are respectively:

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
$22.5^\circ, 67.5^\circ$

Complementary Angles Definition

Two angles are complementary if the sum of their measures is exactly $90^\circ$.

Setting Up the Equation

Let the measure of one angle be $x$. Since the angles are complementary, the measure of the other angle is $90^\circ - x$.

The problem states that the measure of an angle is three times the measure of its complement. We can write this relationship as an equation:

$x = 3 \times (90^\circ - x)$

Solving for the Angle Measure

  1. Distribute the 3 on the right side of the equation:
    $x = 270^\circ - 3x$
  2. Add $3x$ to both sides to gather the $x$ terms:
    $x + 3x = 270^\circ$
    $4x = 270^\circ$
  3. Divide by 4 to solve for $x$:
    $x = \frac{270^\circ}{4}$
    $x = 67.5^\circ$

Finding Both Angles

We found one angle to be $x = 67.5^\circ$.

The measure of its complement is $90^\circ - x = 90^\circ - 67.5^\circ = 22.5^\circ$.

So, the two angles are $22.5^\circ$ and $67.5^\circ$.

We can check: Is $67.5^\circ$ three times $22.5^\circ$? Yes, $3 \times 22.5^\circ = 67.5^\circ$.

This matches option B.

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Important Questions from Lines and Angles

  1. If angles of a triangle are in the ration of 2 : 3 : 4, then the measure of the smallest angle is:

  2. In the triangle, if AB = AC and ∠ABC = 72°, then ∠BAC is:

  3. The angles of a triangle are (8x - 15)°,(6x - 11)° and ( 4x – 10)°. What is the value of x ?

  4. In a ΔABC, the bisectors of ∠B and ∠C meet at point O, inside the triangle. If ∠BOC = 122°, then the measure of ∠A is:

  5. In ΔABC, D is a point on side BC such that ∠ADC = 2∠BAD. If ∠A = 80° and ∠C = 38°, then what is the measure of ∠ADB? 

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