NCERT Exemplar Solutions
Class 10 - Mathematics - CHAPTER 11: Area Related To Circles - Exercise 11.1
Question 3

Question.  3

If the circumference of a circle and the perimeter of a square are equal, then

(A)

Area of the circle = Area of the square

(B)

Area of the circle > Area of the square

(C)

Area of the circle < Area of the square

(D)

Nothing definite can be said about the relation between the areas

Detailed Answer with Explanation:

Step 1: Let the radius of the circle be r (in metres).

Then, circumference of the circle = \(2 \pi r\) metres.

Step 2: Let the side of the square be a (in metres).

Then, perimeter of the square = \(4a\) metres.

Step 3: It is given that circumference of the circle = perimeter of the square.

So, \(2 \pi r = 4a\).

Step 4: Solve for a:

\(a = \dfrac{2 \pi r}{4} = \dfrac{\pi r}{2}\).

Step 5: Find the area of the circle:

Area of circle = \(\pi r^2\) (square metres).

Step 6: Find the area of the square:

Area of square = \(a^2 = \left(\dfrac{\pi r}{2}\right)^2 = \dfrac{\pi^2}{4}r^2\) (square metres).

Step 7: Compare the two areas:

  • Circle: \(\pi r^2\)
  • Square: \(\dfrac{\pi^2}{4} r^2\)

Step 8: Numerical values:

\(\pi \approx 3.14\).

\(\dfrac{\pi^2}{4} \approx \dfrac{9.87}{4} = 2.47\).

So, \(3.14 r^2 > 2.47 r^2\).

Final Step: The area of the circle is greater than the area of the square.

Correct Option: (B)

NCERT Exemplar Solutions Class 10 – Mathematics – CHAPTER 11: Area Related To Circles – Exercise 11.1 | Detailed Answers