An open-top cylindrical tank with a volume of 2000 cubic meters is to be constructed using steel. The steel used for the top and bottom costs 0.5 dollars per square meter, while the steel used for the sides costs 0.3 dollars per square meter. Determine the dimensions of the tank that will minimize the cost of steel used.

Calculus: Early Transcendentals
8th Edition
ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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using the info below 

 

Problem:

An open-top cylindrical tank with a volume of 2000 cubic meters is to be constructed using steel. The steel used for the top and bottom costs 0.5 dollars per square meter, while the steel used for the sides costs 0.3 dollars per square meter. Determine the dimensions of the tank that will minimize the cost of steel used.

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Step 3: State the variables of the problem

Variables:

  • r: radius of the base of the cylinder in meters
  • h: height of the cylinder in meters

Function: The surface area of the cylindrical tank is given by: A = 2πrh + 2πr2

The cost of steel is given by: C = 0.5(2πr 2) + 0.3(2πrh)

Objective: Minimize the cost of steel C.

Domain:

r and h must be positive numbers. Additionally, since the tank has a volume of 2000 cubic meters, we can use the volume formula for a cylinder to set up an equation relating r and h:

V = πr2h = 2000

Therefore, the domain for r is (0, ∞) and the domain for h is (0, 2000/(πr2)).

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Step 4: Solve the above stated problem

Solution:

Using the equation V = πr2h = 2000, we can solve for h in terms of r: h = 2000/(πr2 )

Substituting h into the cost equation, we get:

C = 0.5(2πr 2) + 0.3(2πr(2000/(πr 2)))

C =  πr 2 + 1200/r

Taking the derivative of C with respect to r, we get:

C' = 2πr - 1200/r 2

Setting C' to zero, we get: 2πr = 1200/r 2

Solving for r, we get: r = (600/π)(1/3)

Substituting r back into the equation for h, we get:

h = 2000/(π((600/π)(2/3)))

Therefore, the dimensions of the cylindrical tank that minimize the cost of steel used are approximately:

r = 5.7588 meters h =  19.1961 meters

Thus, the minimum cost of steel used is:

C = π(5.7588) 2 + 1200/19.1961

C ≈ $166.6998

 
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Solution

The minimum cost of the steel required is

$ 166. 70

and the rest are attached on the photo 
Step 1: Given
Volume of cylindercal tank = 2000 m³ Let radius = rm, height = h m
Step 2: Explanation
r²h = 2000 ⇒ h =
2000
π²
...i
Volume of cylindrical tank = 2000
Cost of top and bottom 1 m² area = $0.5Total cost of top and bottom = 0.52nr² = r² Area of sides = 2πrhСos o
Total cost of cylinder = C ⇒ C = r² +0.6h ⇒ Сx = r² +0.6² ⇒ Cx = : Tr² +
1200
2000
π²
r
Take derivative with repect to r
1200
⇒ C'x = =nr² +
dr
2πr -
⇒ С'x =
Put C'(x)=0
⇒ C"x = 2n-1200-2²
⇒ C"x = 2π-1200-2r-²-1
2400
⇒ C"x = 2πt +
3
Atr=
1200
1200
6003
⇒ C²x = 2πr - = 0⇒ 2² = 12 ⇒ 2m³ = 1200⇒ r =
Now take second derivative with respect to r of C(r)
d
1200
⇒ C"x==
= 2πr-
dr
dr
6003
Ar r=
⇒ C"x = 2π +
Solution
1200
1
6003
dr
π
2400
600
TT
dr
dx
5.7588 m Height h
> 0 So cost is minimum at r=
Conclusion
Hence
Minimize cost of steel is $312.56
= nx²-1
2000
600
1
600 3
TI
'm
19.1961 mMinimum cost = ² +
1200
r
6003
⇒ С= n°
TI
+
1200
600
ī
$312.56nearest
Transcribed Image Text:Step 1: Given Volume of cylindercal tank = 2000 m³ Let radius = rm, height = h m Step 2: Explanation r²h = 2000 ⇒ h = 2000 π² ...i Volume of cylindrical tank = 2000 Cost of top and bottom 1 m² area = $0.5Total cost of top and bottom = 0.52nr² = r² Area of sides = 2πrhСos o Total cost of cylinder = C ⇒ C = r² +0.6h ⇒ Сx = r² +0.6² ⇒ Cx = : Tr² + 1200 2000 π² r Take derivative with repect to r 1200 ⇒ C'x = =nr² + dr 2πr - ⇒ С'x = Put C'(x)=0 ⇒ C"x = 2n-1200-2² ⇒ C"x = 2π-1200-2r-²-1 2400 ⇒ C"x = 2πt + 3 Atr= 1200 1200 6003 ⇒ C²x = 2πr - = 0⇒ 2² = 12 ⇒ 2m³ = 1200⇒ r = Now take second derivative with respect to r of C(r) d 1200 ⇒ C"x== = 2πr- dr dr 6003 Ar r= ⇒ C"x = 2π + Solution 1200 1 6003 dr π 2400 600 TT dr dx 5.7588 m Height h > 0 So cost is minimum at r= Conclusion Hence Minimize cost of steel is $312.56 = nx²-1 2000 600 1 600 3 TI 'm 19.1961 mMinimum cost = ² + 1200 r 6003 ⇒ С= n° TI + 1200 600 ī $312.56nearest
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