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Radius of big semi circle R= 30cm

Radius of small circle = r

3r = 30

(a)  r = 10cm

(b) Area of big semi circle = (πR2 )/2 = (3.14 x 30 x 30) / 2 = 1413 

Area of 1 small semi circles = (πr2 )/2 = (3.14 x 10 x 10) / 2 = 157

Area of 7 small semi circles = 7 x  (πr2 )/2 = 7 x  157 = 1099

Area in between the small circles within the big semi-circle, A = 1413-1099 = 314

Therefore, area of shaded region

= one part of A(there are 3 parts)  + one small semi circle

= 314/3 + 157

= 261.7 cm2 (to 1 decimal place)

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