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How many positive integers n satisfy $\lfloor \sqrt[3]{n} \rfloor = 5$?

 Aug 1, 2022
 #2
avatar+2668 
0

Only 3 does. 

 Aug 1, 2022
 #3
avatar+580 
+1

Hey BuilderBoi, 

 

I have a question...

 

How is it 3?

 

Using the floor rule Ifn=xthenxn

 

We get 53n<6

 

That is 125n<216

 

-Vinculum

Vinculum  Aug 1, 2022
edited by Vinculum  Aug 1, 2022
 #4
avatar+2668 
0

Oh, wait that's a cube root...

 

Yea, you're right, I thought it meant n3 not 3n

BuilderBoi  Aug 1, 2022
 #5
avatar+130466 
+2

$3n=5$

 

Note that     (125)^(1/3)  =  5

And that      (216)^(1/3)  = 6

 

So....the number of positive integers that satisfy this  =     215 - 125 + 1 =  91

 

 

cool cool cool

 Aug 1, 2022

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