Posted by Bob on Monday, April 29, 2013 at 11:35am.
How many 4 digit positive integers have the ones digit a multiple of 1, the tens digit a multiple of 2, the hundreds digit a multiple of 3 and the thousands digit a multiple of 4?

Math (Combinatorics)  Steve, Monday, April 29, 2013 at 2:01pm
(2)(4)(5)(10)=400

Math (Combinatorics)  Anirudh Mahapatro, Friday, May 3, 2013 at 4:25am
400