Answer:
- radius: 1.84 in
- height: 3.68 in
Step-by-step explanation:
After you've worked a couple of "optimum cylinder" problems, you find that the cylinder with the least surface area for a given volume has a height that is equal to its diameter. So, the volume equation becomes ...
V = πr²·h = 2πr³ = 39 in³
Then the radius is ...
r = ∛(39/(2π)) in ≈ 1.83779 in ≈ 1.84 in
h = 2r = 3.67557 in ≈ 3.68 in
_____
The total surface area of a cylinder is ...
S = 2πr² + 2πrh
For a given volume, V, this becomes ...
S = 2π(r² +r·(V/(πr²))) = 2πr² +2V/r
The derivative of this with respect to r is ...
S' = 4πr -2V/r²
Setting this to zero and multiplying by r²/2 gives ...
0 = 2πr³ -V
r = ∛(V/(2π)) . . . . . . . . looks a lot like the expression above for r
__
If we substitute the equation for V into the equation just above this last one, we have ...
0 = 2πr³ - πr²·h
Dividing by πr² gives ...
0 = 2r - h
h = 2r . . . . . generic solution for cylinder optimization problems
Answer:
![\huge{\purple {r= 2\times\sqrt[3]3}}](https://tex.z-dn.net/?f=%5Chuge%7B%5Cpurple%20%7Br%3D%202%5Ctimes%5Csqrt%5B3%5D3%7D%7D)
![\huge 2\times \sqrt [3]3 = 2.88](https://tex.z-dn.net/?f=%5Chuge%202%5Ctimes%20%5Csqrt%20%5B3%5D3%20%3D%202.88)
Step-by-step explanation:
- For solid iron sphere:
- radius (r) = 2 cm (Given)
- Formula for
is given as:
- For cone:
- r : h = 3 : 4 (Given)
- Let r = 3x & h = 4x
- Formula for
is given as:
- It is given that: iron sphere is melted and recasted in a solid right circular cone of same volume

![\implies \huge{\purple {r= 2\times\sqrt[3]3}}](https://tex.z-dn.net/?f=%5Cimplies%20%5Chuge%7B%5Cpurple%20%7Br%3D%202%5Ctimes%5Csqrt%5B3%5D3%7D%7D)
- Assuming log on both sides, we find:
- Taking antilog on both sides, we find:
Answer:
2
Step-by-step explanation:all of them can be divided by 2 and it is the smallest number.