|lifted from Elizabeth Richards|
He likes the above image because it has animals, but the number line is not "real" because it doesn't have arrows.
So far nearly every time I've drawn a number line, I've included arrows on the ends symbolizing infinity in either direction. It's an old habit from high school and college algebra. Now Colin won't accept any number line without arrows.
Here's the one he liked best that I found online:
|lifted from Smart Exchange|
Seriously. The absence of numbers does not matter to Colin. As long as it has points and arrows on both ends, he is very happy.