The ten's digit in $1 !+4 !+7 !+10 !+12 !+13 !+15 !+16 !+17 !$ is divisible by

The ten's digit in $1 !+4 !+7 !+10 !+12 !+13 !+15 !+16 !+17 !$ is divisible by
  1. 4 !
  2. 3 !
  3. 5 !
  4. 7 !

Solution

$\begin{gathered} \text { } 1 !+4 !+7 !=1+24+5040 \\ 1 !+4 !+7 !=5065 \\ (10 !+12 !+\ldots+17 !) \text { this value } \end{gathered}$ have last 2 digits as zero es So, $10^{\prime}$ 's digit of given question is same as $10^{\prime} \mathrm{s}$ digit of $(1 !+4 !+7 !)$ $\therefore$ Required 10 's digit is $6=3$ ! Hence, option (1) is correct.

Asked in: AP EAMCET 2020 (22 Sep Shift 2)

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