Respuesta :
Answer:
h = 28/πr² or 28/(π((14/π)^⅔))
r = (14/π)^⅓
Explanation:
Given
Let r = radius, h = height of the cylinder
Volume, V =28in³
V = πr²h ----- volume of a cylinder
πr²h = 28 --- make h the subject of formula
h = 28/πr²
Area of the the cylinder is;
A = 2πr² + 2πrh
Substitute 28/πr² for h to get area in terms of radius
A = 2πr² + 2πr(28/πr²)
A = 2πr² + 56/r
Differentiate A with respect to r
dA/dr = 4πr - 56/r²
Set dA/dr to 0 (.....using the least amount of metal)
4πr - 56/r² = 0
(4πr³ - 56)/r² = 0 --- Multiply through by r²
4πr³ - 56 = 0
4πr³ = 56 --- make r the subject of formula
r³ =56/4π
r³ = 14/π
r = (14/π)^⅓
h = 28/πr²
h = 28/(π((14/π)^⅔))
The radius and height of a container if it has a capacity of 28 in.3 and is constructed using the least amount of metal are:
- h = 28/πr² or 28/(π((14/π)^⅔)).
- r = (14/π)^⅓
Calculations and Parameters:
Given that:
- r = radius,
- h = height of the cylinder
- Volume, V =28in³
Then, we know that
V = πr²h ----- volume of a cylinder
πr²h = 28 ---
If we make h the subject of the formula
h = 28/πr²
Area of the cylinder is;
A = 2πr² + 2πrh
Substitute 28/πr² for h to get the area in terms of radius
- A = 2πr² + 2πr(28/πr²)
- A = 2πr² + 56/r
Differentiate A with respect to r
dA/dr = 4πr - 56/r²
If we set dA/dr to 0 (.....using the least amount of metal)
- 4πr - 56/r² = 0
- (4πr³ - 56)/r² = 0 --- Multiply through by r²
- 4πr³ - 56 = 0
- 4πr³ = 56 --- make r the subject of formula
- r³ =56/4π
- r³ = 14/π
- r = (14/π)^⅓
Then
h = 28/πr²
h = 28/(π((14/π)^⅔))
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