I Need Scissors 61!

What is the last digit of 61 ! 61! \, ?

Notation :
! ! denotes the factorial notation. For example, 8 ! = 1 × 2 × 3 × × 8 8! = 1\times2\times3\times\cdots\times8 .


The answer is 0.

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3 solutions

Bloons Qoth
Aug 13, 2016

5 ! 5! will already give us 120 120 . Any positive integers we multiply by 120 120 will have a unit digit of 0 0

Therefore 61 ! 61! will have a unit digit of 0 \color{#BA33D6}{\boxed{0}}

Matin Naseri
Feb 17, 2018

Very easy.

the last digit of every number n > 4 \text{ n > 4 } always is 0 \boxed{0}

\therefore{} the last digit of 61! \text{61!} is 0 \boxed{0} .

Sam Bealing
May 2, 2016

61 ! = 1 × 2 × 3 × 4 × 5 × × 61 61!= 1\times 2 \times 3 \times 4 \times 5 \times \cdots \times 61

2 61 ! , 5 61 ! 10 61 ! 2 \vert 61!, 5 \vert 61! \Rightarrow 10 \vert 61!

The last digit is therfore 0 \boxed{0}

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