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Answer :
Radius of the quadrant \( = \ OB = \sqrt{OA^2 \ + \ AB^2} \ \)
\( = \sqrt{20^2 \ + \ 20^2} \ \)
\( = \ 20 \sqrt{2} \) cm
\(\therefore \) Area of quadrant OPBQ
\(= \ \frac{1}{4} \ \pi r^2 \ \)
\( = \ \frac{1}{4} \ × \ 3.14 \ × \ (20 \sqrt{2})^2 \ \)
\( = \frac{1}{4} \ × \ 3.14 \ × \ 800 \ \)
\( = \ 628 \) cm2
Area of the square OABC
\(= \ (20)^2 \ = \ 400 \) cm2
So, area of the shaded region
= Area of quadrant - Area of square OABC
\( = \ 628 \ - \ 400 \ = \ 228 \) cm2