How old was your child when they learned to ride a bike without training wheels?

[Marian's mommy]

I was 5 when I learned how and my husband said he was 6. But my son who will turn 9 next month just learned how in the past couple of months. Is this kind of late or is it average? He doesn't have any physical problems that would have prevented him from learning and he's always had a bike to practice on. Also, now that he's learned how to ride, and his birthday is next month we are looking at a new bike for him. What size would be right. He is a little small for his age. But I measured him up against a 20" at walmart and he was able to sit on the seat with his feet flat on the ground but a 20" just seems too big.

And just curious, what age did you learn to ride a bike without training wheels?