Assertion (A) : If three angles of a quadrilateral are `130^@,70^@` and `60^@` then the fourth angle is `100^@`
Reason(R) : The sum of all the angle of a quadrilateral is `360^@`
The correct answer is : (a) /(b)/(c )/(d).

Options

A. Both Assertion (A) and Reason (R ) are true and Reaoson (R ) is a correct explanation of Assertion (A) .
B. Both Assertion (A) and Reason (R ) are true but Reason (R ) is not a correct explanation of Assertion (A).
C. Assertion (A) is true and Reason (R ) is false.
D. Assertion (A) is false and Reason (R ) is true.

Answer

To solve the problem, we need to verify the assertion and the reason provided in the question.

### Step-by-Step Solution:

1. **Identify the Given Angles**:
We have three angles of a quadrilateral:
- Angle 1 = 130°
- Angle 2 = 70°
- Angle 3 = 60°

2. **Use the Property of Quadrilaterals**:
The sum of all interior angles of a quadrilateral is always 360°.

3. **Set Up the Equation**:
Let the fourth angle be represented as \( x \). According to the property mentioned, we can write the equation:
\[ x + 130° + 70° + 60° = 360° \]

4. **Combine the Known Angles**:
First, add the known angles together:
\[ 130° + 70° + 60° = 260° \]

5. **Substitute and Solve for \( x \)**:
Now substitute the sum of the known angles back into the equation:
\[ x + 260° = 360° \]
To find \( x \), subtract 260° from both sides:
\[ x = 360° - 260° = 100° \]

6. **Conclusion**:
The fourth angle is \( 100° \). Therefore, the assertion that the fourth angle is \( 100° \) is correct.

7. **Evaluate the Reason**:
The reason states that the sum of all angles in a quadrilateral is \( 360° \), which is a true statement.

8. **Final Assessment**:
Both the assertion and the reason are true, and the reason correctly explains the assertion.

### Answer:
The correct answer is: (a) Both assertion and reason are true, and the reason is a correct explanation of the assertion.

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