If the angles are in the ratio `5 : 3 : 7,` then the triangle is

Options

A. an acute angled triangle
B. an obtuse angled triangle
C. a right angled triangle
D. an isosceles triangle

Explanation

To determine the type of triangle based on the given ratio of its angles, follow these steps:

### Step-by-Step Solution:

1. **Understand the Ratio of Angles**: The angles of the triangle are given in the ratio 5:3:7. This means we can express the angles in terms of a variable \( x \).
- Let the angles be \( 5x \), \( 3x \), and \( 7x \).

2. **Use the Triangle Angle Sum Property**: The sum of the angles in any triangle is always \( 180^\circ \).
- Therefore, we can write the equation:
\[ 5x + 3x + 7x = 180^\circ \]

3. **Combine Like Terms**: Combine the terms on the left side of the equation.
- This gives us:
\[ 15x = 180^\circ \]

4. **Solve for \( x \)**: To find the value of \( x \), divide both sides of the equation by 15.
- Thus:
\[ x = \frac{180^\circ}{15} = 12^\circ \]

5. **Calculate Each Angle**: Now substitute \( x \) back into the expressions for the angles:
- First angle: \( 5x = 5 \times 12 = 60^\circ \)
- Second angle: \( 3x = 3 \times 12 = 36^\circ \)
- Third angle: \( 7x = 7 \times 12 = 84^\circ \)

6. **Classify the Triangle**: Now that we have all three angles:
- \( 60^\circ \), \( 36^\circ \), and \( 84^\circ \).
- Since all angles are less than \( 90^\circ \), the triangle is classified as an **acute triangle**.

### Conclusion:
The triangle with angles in the ratio \( 5:3:7 \) is an **acute angle triangle**.