the length and breadth of a book is 40cm and 20 cm respectively . find its area in dm^2
Answers
Answer:
Solution:-
Let the radius of the top part be 'R' and radius of the bottom part be 'r' respectively.
Diameter (Top) = 40 cm
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