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When you pick an integer from $1$ to $50$, how many cases are there that you pick a multiple of $4$ or $13$?

I thought maybe that if I counted by $4$: ($4+4 = 8$, $8+4=12$, etc) would will work, and I tried doing to same with $13$, but it didn't work. What am I doing wrong?

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    $\begingroup$ $12*4=48$, so $12$ numbers are multiple of $4$ and $13*4=52>50$ so $3$ numbers multiple of $13$ $\endgroup$ – Vikram Mar 2 '15 at 3:35
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Req. Multiples of 4: 4,8,12,16,20,24,28,32,36,40,44,48 -> 12 Req. Multiples of 13: 13,26,39 -> 3

Therefore number of cases are 12 + 3 = 15 cases.

Note: If it's probability you're looking for, then that would be 15/50 = 3/10

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