I have a number machine. I say x gives y if when x goes in, y comes out. For any numbers x and y, by "xy" I mean x followed by y. Here are my two rules.

1x gives x.
For example, 13 gives 3.
If x gives y, then 2x gives yy.
For example, 213 gives 33 since 13 gives 3.

What is a number that gives itself?

(In reply to solution by joy)

You are so right. I came up with 2 as well. How 2121 works is beyond me. Going right to left, the first 2 gives 11. Crazy, I'm just saying.

Posted by Lawrence on 2003-08-24 16:34:22