Question

In the given figure, sectors of two concentric circles of radii 3.5 cm and 1.75 cm are shown, then the area of the shaded region is​

Answer 1

Given: The radii of the sectors of two concentric circles 3.5 cm and 1.75 cm

           The angle subtended at the centre of the circle = 30°

To find: The area of the shaded region as given in the figure

Solution:

The area of the sector of a circle is given by the formula = θ/360 × $\pi$ × r²

(where θ is the angle subtended at the centre of the circle by the sector

and r is the radius of the sector)

Therefore, the area of the smaller sector

= 30/360 × $\pi$ × (1.75)²

= 1/12 × 22/7 × 1.75 × 1.75

= 1/6 × 11 × 0.25 × 1.75

= 0.802 cm²

Now the area of the larger sector

= 30/360 × $\pi$ × (3.5)²

= 1/12 × 22/7 × 3.5 × 3.5

= 1/6 × 11 × 0.5 × 3.5

= 3.208 cm²

Hence, the area of the shaded region = (3.208 - 0.802) cm²

                                                               = 2.406 cm²

Answer: 2.406 cm²

Answer 2

Answer:

Ans−OptionD.

Step-by-step explanation:

=9.625cm