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Question

Two angles are complementary. The measure of one angle is 10 degrees more than three times the measure of the other angle. What is the measure of the smaller angle?

This question was previously asked in
SSC CGL 2025 Tier 2 Paper 1 Question Paper (19-Jan-2026)
The correct answer is
$20^\circ$

Solving Complementary Angles Algebraically

Two angles are complementary if their sum is equal to 90 degrees. Let the measures of the two angles be '$x$' and '$y$'.

From the problem statement, we have the following conditions:

  • The angles are complementary: $x + y = 90^\circ$.
  • One angle's measure is 10 degrees more than three times the other: Let $x = 3y + 10^\circ$.

Step-by-Step Solution

  1. Substitute the expression for '$x$' from the second condition into the first equation:

    $(3y + 10^\circ) + y = 90^\circ$

  2. Combine like terms:

    $4y + 10^\circ = 90^\circ$

  3. Isolate the term with '$y$' by subtracting $10^\circ$ from both sides:

    $4y = 90^\circ - 10^\circ$

    $4y = 80^\circ$

  4. Solve for '$y$' by dividing both sides by 4:

    $y = \frac{80^\circ}{4}$

    $y = 20^\circ$

  5. Find the measure of the other angle, '$x$':

    $x = 3y + 10^\circ = 3(20^\circ) + 10^\circ = 60^\circ + 10^\circ = 70^\circ$

  6. Identify the smaller angle. The two angles are $20^\circ$ and $70^\circ$. The smaller angle is $20^\circ$.

Therefore, the measure of the smaller angle is $20^\circ$.

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