All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Numbers
Ending by 3 or 7 (Posted on 2016-08-01) Difficulty: 2 of 5
Any number ending by 3 or 7 must have at least one factor ending by 3 or 7.
Prove the above statement.

See The Solution Submitted by Ady TZIDON    
No Rating

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution q.e.d. Comment 1 of 1
Create a Mod 10 multiplication table.

The only way to get a 3 is 1*3 or 7*9
The only way to get a 7 is 1*7 or 3*9

Since all of these contain a 3 or a 7, we are proved.

  Posted by Steve Herman on 2016-08-01 08:49:12
Please log in:
Remember me:
Sign up! | Forgot password

Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (3)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Copyright © 2002 - 2018 by Animus Pactum Consulting. All rights reserved. Privacy Information