4. How many zeroes does the number $50 \times 49 \times 48 \times \cdots \times 3 \times 2 \times 1$ end with?
(a) 8 ;
(b) 9 ;
(c) 10 ;
(d) 11;
(e) 12 .
4 Ans: (e).
By counting the number of factor 5 in the product, we easily see that the number 50 ! ends with $\frac{50}{5}+\frac{50}{25}=12$ zeros.