NCERT Exemplar Solutions
Class 10 - Mathematics - CHAPTER 11: Area Related To Circles - Exercise 11.4
Question 17

Question. 17

Find the area of the shaded region shown in Fig. 11.20.

Fig. 11.20 (square of side 14 cm with a 4-petal shape made of four semicircles of radius 3 cm cut out)

Answer:

\(196 - 18\pi\,\text{cm}^2 \;\approx\; 139.5\,\text{cm}^2\)

Detailed Answer with Explanation:

Step 1: The outer shape is a square of side \(14\,\text{cm}\).

Area of square = side × side = \(14 \times 14 = 196\,\text{cm}^2\).

Step 2: Inside the square, there is a flower-like figure made by 4 semicircles.

Each semicircle has radius \(3\,\text{cm}\).

Step 3: Area of one semicircle = \(\tfrac{1}{2} \pi r^2\).

= \(\tfrac{1}{2} \pi (3^2) = \tfrac{1}{2} \pi \times 9 = 4.5\pi\,\text{cm}^2\).

Step 4: There are 4 such semicircles.

Total area of 4 semicircles = \(4 \times 4.5\pi = 18\pi\,\text{cm}^2\).

Step 5: The shaded region is the square area minus the 4 semicircles area.

Shaded area = \(196 - 18\pi\,\text{cm}^2\).

Step 6: Approximating \(\pi \approx 3.14\):

\(18 \pi = 18 \times 3.14 = 56.52\,\text{cm}^2\).

Shaded area = \(196 - 56.52 = 139.48 \approx 139.5\,\text{cm}^2\).

Final Answer: \(\mathbf{139.5\,\text{cm}^2}\)

NCERT Exemplar Solutions Class 10 – Mathematics – CHAPTER 11: Area Related To Circles – Exercise 11.4 | Detailed Answers