Five digits and one
Here is a nice place value puzzle I saw on the Maths is Fun website.
I am thinking of a five digit number. If you were to put a "1" at the end of the number you would get a six digit number which is three times the six digit number you get by placing a "1" at the front of my number. What number am I thinking of?
Maths is Fun - math and logic puzzles appropriate for math education.