The answer of this problem because I am currently having trouble with this topic and teach me how to solve it thanks!

[25 POINTS] A cylinder has a volume of 400π cm3. Find the dimensions that minimize its surface area.

miss Akunina [59]

Answer:

r = 5.848cm, h = 11.696cm

Step-by-step explanation:

Surface area: $SA=2\pi rh+2\pi r^2$

Volume: $V=\pi r^2h$

Therefore, the height of a cylinder given its volume would be $h=\frac{V}{\pi r^2}$ , thus:

$SA=2\pi r(\frac{V}{\pi r^2})+2\pi r^2\\\\SA=\frac{2V}{r}+2\pi r^2\\\\SA=\frac{2(400\pi)}{r}+2\pi r^2\\\\SA=\frac{800\pi}{r}+2\pi r^2$

We now find the derivative of the surface area of the cylinder with respect to its radius and set it equal to 0, solving for the radius:

$\frac{d(SA)}{dr}=-\frac{800\pi}{r^2}+4\pi r$

$0=-\frac{800}{r^2}+4\pi r$

$0=800\pi+4\pi r^3$

$-800\pi=4\pi r^3$

$-200=r^3$

$r\approx5.848$

If $0If [tex]r>5.848$ , then the surface area of the cylinder increases

Therefore, the surface area is minimized when the radius is $r=5.848cm$ , making the minimum height $h=\frac{V}{\pi r^2}=\frac{400\pi}{\pi(5.848)^2}\approx11.696cm$ .

In conclusion, the 2nd option is correct.

3 0

2 years ago

How do I solve these systems of equations?

ruslelena [56]

1. -x+9y=-5
x-5y=1
-----------------
x=1+5y
-(1+5y)+9y=-5
-1-5y+9y=-5
-1+4y=-5
4y=-5-(-1)
4y=-5+1=-4
4y=-4
y=-4/4=-1
So x=1+5y=1+5(-1)=1-5=-4
Answer: x=-4, y=-1. (-4, -1).

2) -7x-y=13
8x+y=-14
------------------
y=-14-8x
-7x-(-14-8x)=13
-7x+14+8x=13
14+x=13
x=13-14=-1
y=-14-8(-1)=-14+8=-6.
Answer: x=-1, y=-6. (-1, -6).

3) x+7y=24
x-9y=-24
----------------
x=24-7y
24-7y-9y=-24
24-16y=-24
16y=24-(-24)=24+24=48
y=48/16=3
x=24-7(3)=24-21=3
Answer: x=3, y=3. (3, 3).

4). 3x+y=-21
x+y=-5
-------------------
x=-5-y
3(-5-y)+y=-21
-15-3y+y=-21
-15-2y=-21
2y=-15-(-21)=-15+21=6
y=6/2=3
x=-5-3=-8.
Answer: x=-8, y=3. (-8, 3).

5) 3x+6y=6
9x-12y=18
---------------
Simplify 3x+6y=6 will get you x+2y=2,
x=2-2y,
9(2-2y)-12y=18
18-18y-12y=18
18-30y=18
30y=18-18=0
y=0/30=0
x=2-2(0)=2-0=2
Answer: x=2, y=0. (2, 0).

6) 6x+8y=26
-7x+2y=-19
-----------------
-4(-7x+2y)=-4(-19)
28x-8y=76
---------------------------
6x+8y=26
28x-8y=76
-----------------
34x=102
x=102/34=3
6(3)+8y=26
18+8y=26
8y=26-18=8
y=8/8=1
Answer: x=3, y=1. (3, 1)

BONUS:
-5x+5y=-25
3x+2y=10
---------------
Simplify -5x+5y=-25 you will get x-y=5
x=y+5
3(y+5)+2y=10
3y+15+2y=10
5y+15=10
5y=10-15=-5
y=-5/5=-1
x=-1+5=4
Answer: x=4, y=-1. (4, -1).

6 0

3 years ago

Show me how to work the equation 30-f+8f=30

ELEN [110]

30-f+8f=30

30+7f=30

Move +30 to the right side. Sign changes from +30 to -30.

30-30+7f=30-30

7f=0

Divde by 7

7f/7=0/7

Cross out 7 and 7, divide by 7. Becomes 1*1*f=f

f=0

Answer: f=0

4 0

3 years ago

Read 2 more answers

Please help me with this

Lisa [10]

100%-26%
426000*(1-0.26)^t, yearly
(0.74^(1/12))=0.74^0.083 monthly rate of decrease
Equation for calculation population
426000*(0.74^0.083)^12t

I think it should look like this 0.74^0.083 monthly rate of decrease

5 0

4 years ago

Read 2 more answers

You are making cupcakes and the recipe specifies 6 small eggs for every 27 cupcakes. You need to make 36 cupcakes. How many smal

astra-53 [7]

For every egg you can make 4.5 cupcakes so you will need 8 small eggs because 8 times 4.5 equals 36

6 0

3 years ago