Have you heard of central binomial coefficient?

Which of these number is larger?

10 ! 10! 5 ! × 5 ! × 5 ! 5!\times5!\times5!

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2 solutions

Prokash Shakkhar
Jan 8, 2017

If we use "\color\pink{?}" as relational operator, we get...

( 10 ! ? 5 ! 5 ! 5 ! ) (10! \: ?\: 5! * 5! *5!) l o g 10 ( 10 ! ) ? l o g 10 ( 5 ! ) + l o g 10 ( 5 ! ) + l o g 10 ( 5 ! ) \Rightarrow {log_{10}(10!)}\:?\: {log_{10} (5!) +log_{10}(5!)+ log_{10}(5!)}

l o g ( 10 ) + l o g ( 9 ) + + l o g ( 1 ) ? 3 l o g ( 5 ) + l o g ( 4 ) + + l o g ( 1 ) \Rightarrow{ log(10)+log(9)+\ldots +log(1)}\:?\: 3{ log (5)+log(4)+\ldots +log(1)} \: l o g ( 10 ) + l o g ( 9 ) + + l o g ( 1 ) ? 3 l o g ( 5 ) + l o g ( 4 ) + + l o g ( 1 ) \Rightarrow\left \lfloor{log(10)}\right\rfloor+\left\lfloor{log(9)}\right\rfloor+…+\left\lfloor{log(1)}\right\rfloor \:?\: 3{\left \lfloor {log(5)}\right\rfloor+\left\lfloor{log(4)}\right\rfloor+… +\left\lfloor{log(1)} \right \rfloor} 1 + 0 + 0 + 0 ? 3 ( 0 + 0 + + 0 ) \Rightarrow 1+0+0……+0 \:?\: 3(0+0+……+0) 1 > 0 \Rightarrow 1>0

So, it can be said that, \boxed{\color\red{10! \: > (5!)^3}}

Michael Williams
Nov 10, 2017

We can write 5! as 5 * 4 * 3 * 2 * 1, and 10! as 10 * 9 * 8... * 1. Thus, 3 * 5! is 3 * 5 * 4 * 3... * 1. because 10 is greater than 5, 10! as all of the factors that 5! does. 10! can be written as 10 9 * 8... * 6 * 5!. Since each of the factors 10...6 is greater than 3, and since the factors 5...1 all cancel out, it is clear that 10! must be greater than 3 5!.

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