SAT problem of the week, October 06, 2014

An integer x has n zeros at the end if and only if it is divisible by 10^n . For example, 12,500,000 is divisible by 10^5 but not by 10^6 .

How many zeros are at the end of 1 \times 2 \times 3 \times \cdots \times 100?

  1. 1 (check answer)
  2. 3 (check answer)
  3. 10 (check answer)
  4. 20 (check answer)
  5. 24 (check answer)

Solutions, hints, and questions are welcomed. A full solution will be posted on October 12th. If you would like to learn how to enter math formulas into this blog, visit the WordPress LaTeX tutorial page.