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Let $N$ be the units digit of the number $21420N$. Which nonzero value of $N$ makes this number divisible by $6$?

 Mar 30, 2020
 #1
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A number is divisible by 6 if it is divisible 3 AND 2.

 

By divisibility of 3 rule:

2 + 1 + 4 + 2 + 0 + N = 9 + N

 

Let us try

N = 3 (nope because it is odd so it can't be divisible by 2)

N = 6 (yes!)

N = 9 (nope)

 Mar 30, 2020

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