Question

Find the last non zero digit of 30!.

• A. 2
• B. 4
• C. 6
• D. 8

Answer 1

The correct option is D 8

Factorize 30! into prime factors. Find the units digit of all the factors individually and multiply to get the units digit of 30!.
$30!=2^{26}\times 3^{14}\times 5^7\times 7^4\times {11}^2\times {13}^2\times {17}^1\times {19}^1\times {23}^1\times {29}^1$
Now, $5^7$ and $2^7$ can be eliminated, since these will result in zeroes.
The units digit of all the remaining factors = 8.