+0  
 
0
90
3
avatar+1998 

May someone explain to me why i was incorrect

 Dec 4, 2020
 #1
avatar+112086 
+1

How can we explain why you were wrong when you have not even given us an outline of your working ?

 Dec 4, 2020
 #2
avatar+112086 
0

To be honest, I have played with this and I do not have an answer.

Melody  Dec 4, 2020
 #3
avatar+114592 
+2

h =  300/ (pi r^2)    →  h^2  =  (90000/ pi^2)r-4

 

Subbing   x for  r   we have  that

 

S   =  (pi * x)  ( x^2  +  (90000/pi^2)x-4 )1/2

 

The Calculus is messy  but this graph  shows  that  there is  no  x = r   that will  produce a max.....only  a  min

 

https://www.desmos.com/calculator/zpyqlutuoq

 

A radius of  ≈  4.07 cm    will produce a minimum surface area  of  ≈ 90.229 cm^2

 

h =  300 / ( pi * 4.072)  ≈  5.76  cm

 

cool cool cool

 Dec 4, 2020

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