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Assertion (A) : If a wire of length 22 c...

Assertion (A) : If a wire of length 22 cm is bent in the shape of a circle, then area of the circle so formed is `40 cm^(2)`
Reason (R) : Circumference of the circle = length of the wire

A

Both A and R are true and R is the correct explanation of A

B

Both A and R are true and R is not correct explanation of A

C

A is true but R is false

D

A is false but R is true

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem step by step, we will analyze the assertion and the reason provided in the question. ### Step 1: Understand the Assertion and Reason - **Assertion (A)**: If a wire of length 22 cm is bent in the shape of a circle, then the area of the circle so formed is 40 cm². - **Reason (R)**: The circumference of the circle = length of the wire. ### Step 2: Establish the Relationship between Length of Wire and Circumference The length of the wire is given as 22 cm. When the wire is bent into the shape of a circle, this length becomes the circumference of the circle. **Formula for Circumference of a Circle**: \[ C = 2\pi r \] Where \( C \) is the circumference and \( r \) is the radius. ### Step 3: Set Up the Equation Since the circumference of the circle is equal to the length of the wire, we have: \[ 2\pi r = 22 \] ### Step 4: Solve for the Radius (r) To find the radius \( r \), we can rearrange the equation: \[ r = \frac{22}{2\pi} = \frac{11}{\pi} \] Using the approximation \( \pi \approx \frac{22}{7} \): \[ r = \frac{11}{\frac{22}{7}} = \frac{11 \times 7}{22} = \frac{77}{22} = \frac{7}{2} \text{ cm} \] ### Step 5: Calculate the Area of the Circle The area \( A \) of a circle is given by the formula: \[ A = \pi r^2 \] Substituting the value of \( r \): \[ A = \pi \left(\frac{7}{2}\right)^2 = \pi \cdot \frac{49}{4} = \frac{49\pi}{4} \] Using \( \pi \approx \frac{22}{7} \): \[ A = \frac{49 \times \frac{22}{7}}{4} = \frac{49 \times 22}{28} = \frac{1078}{28} = 38.5 \text{ cm}^2 \] ### Step 6: Compare the Area with the Assertion The calculated area of the circle is 38.5 cm², which is not equal to the assertion that it is 40 cm². Therefore, the assertion is false. ### Step 7: Evaluate the Reason The reason states that the circumference of the circle is equal to the length of the wire, which is true. ### Conclusion - **Assertion (A)**: False (the area is 38.5 cm², not 40 cm²). - **Reason (R)**: True (the circumference equals the length of the wire). Thus, the final answer is that the assertion is false, but the reason is true. ---
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