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Question

In $\Delta ABC$, if $\angle A = 3\angle B$ and $\angle C = 2\angle B$ then, what are values of $\angle A, \angle B$ and $\angle C$?

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper PDF (31-Jan-2021) (Shift 1)
The correct answer is
$90^\circ$ , $30^\circ$ and $60^\circ$

Solving Triangle Angles A B C

The problem requires finding the measures of the three angles in a triangle, $\angle A$, $\angle B$, and $\angle C$, given specific relationships between them. We know that the sum of the interior angles in any triangle is always $180^\circ$.

Given relationships:
  • $\angle A = 3\angle B$
  • $\angle C = 2\angle B$
Using the triangle angle sum theorem:

The sum of the angles in $\Delta ABC$ is $180^\circ$:

$ \angle A + \angle B + \angle C = 180^\circ $

Substitute the given relationships into the equation to express everything in terms of $\angle B$:

$ (3\angle B) + \angle B + (2\angle B) = 180^\circ $

Combine the terms involving $\angle B$:

$ 6\angle B = 180^\circ $

Solve for $\angle B$:

$ \angle B = \frac{180^\circ}{6} $ $ \angle B = 30^\circ $

Now, calculate $\angle A$ and $\angle C$ using the value of $\angle B$:

  • $\angle A = 3\angle B = 3 \times 30^\circ = 90^\circ$
  • $\angle C = 2\angle B = 2 \times 30^\circ = 60^\circ$

Therefore, the values of the angles are $\angle A = 90^\circ$, $\angle B = 30^\circ$, and $\angle C = 60^\circ$. This matches Option B.

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