9. The figure 17.30 consists of four small semi-circlesof equal radii (each 42 c...

Questions

June 2021 2 14 Report

9. The figure 17.30 consists of four small semi-circles
of equal radii (each 42 cm) the perimeter of the
shaded region is
(a) 524 cm
(c) 396 cm
(6) 264 cm
(d) 504 cm

AngelineSudhagar

Answer:

radii of small semicircles are given ,

r = 42 cm => d = 84 cm

so radius of bigger semicircle.

R = 84 cm

Substitute in the perimeter formula,

Perimeter of 2 semicircle = 2 × πr + 2r

= 2 × 22 × 84 + 2 × 84

= 44 × 84/7 + 168

and then you will arrive at the answer...

DevyaniKhushi

Perimeter of one smaller semicircular shaded region ↓

$\huge = > \frac{ \text{Perimeter of circle}}{2} \\ \\ \huge = > \frac{2\pi r}{2} \\ \\ \huge= > \pi r \\ \\ \huge = > \frac{22}{7} \times 42 \\ \\ \huge= > (22 \times 6 ) \\ \\ \huge= > 132 \: \: \rm cm$