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The length and breadth of a book is 40cm and 20 cm respectively . find its area in dm^2 |
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Answer» ong>Answer: Solution:- Let the radius of the top part be 'R' and radius of the bottom part be 'r' respectively. Radius (R) = 40/2 = 20 cm 10 cm = 1 dm 20 cm = 2dm Diameter (Bottom) = 20 cm Radius (r) = 20/2 = 10 cm 10 cm = 1 dm Height = 12 cm = 1.2 dm Slant height ('l') = √H² + (R - r)² = √(1.2)² + (2 - 1)² = √1.44 + 1 = √2.44 = 1.56 So, slant height (l) is 1.56 dm AREA of the tin sheet used for bucket = Curved surface area of the bucket + Area of the base = π(R + r)*l + πr² ⇒ 3.14*(2 + 1)*1.56 + 3.14*1² ⇒(3.14*3*1.56) + 3.14 ⇒ 14.6952 + 3.14 ⇒ 17.8352 sq dm CSA of the tin sheet used = 17.8352 sq dm Rate of tin sheet = Rs. 1.2 per sq dm Total cost of the tin sheet used for MAKING the bucket = 17.8352*1.2 = Rs. 21.40 Answer. Volume = 1/3πh(R² + r² + R*r) = 1/3*3.14*1.2*(2² + 1² + 2*1) = 1/3*3.14*1.2*7 = 26.376/3 Volume = 8.792 cu dm |
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