This is what my almost-5-year-old daughter said to me on the way to preschool this morning when I asked how many kids were in her preschool class. She was thinking about how many lollipops she might need to bring on her birthday in two days, and I actually know how many kids are in her preschool class but was curious about what she would say.

What she said was, “I don’t know. I’m not very good at counting.”

“Hm,” I said, because I couldn’t just let that statement stand. “How high can you count?”

“Let me tell you!” she said excitedely, and proceeded:

“One, two, three, four, five, six, seven, eight, nine, ten, twelve, thirteen, fourteen, sixteen, seventeen, eighteen, nineteen, seventeen, eighteen, nineteen, twenty, twenty-one, twenty-two, twenty-three, twenty-four, twenty-five, twenty-six, twenty-seven, twenty-eight, twenty-nine, twenty-ten…” Here she trailed off.

“Thirty,” I prompted, and she was off again:

“Thirty-one, thirty-two, thirty-three, thirty-four, thirty-five, thirty-six, thirty-seven, thirty-eight, thirty-nine, twenty!”

“Forty?”

“Forty!”

I won’t try to unpack what my daughter meant when she said she can’t count very well (she probably meant she has never actually counted how many children are in her preschool class, and what preschooler has?). But I can tell you that Anya is actually a fairly competent counter. She’s also an enthusiastic counter, so I don’t feel too worried about this one statement in this one context.

But what she’s not good at is the teens. She’s pretty terrible at the teens, actually. Yet with minimal prompting, she was great at 20 through 40.

When we talk about numeration systems in my History of Mathematics class I give them a list of the English counting words from one to one hundred, and the first thing students notice is that the words for eleven through nineteen are weird. “Sixty-seven” at least suggests the idea of “six tens and seven” but “twelve” is just another word in a sequence of unrelated words.

This means that once children learn the number words from one through ten, they still have to conquer eleven through nineteen by brute force. To learn the numbers from 20 on kids can make use of patterns, but before that it’s pretty much pure memorization.

Ultimately, though, patterns are way more important for understanding mathematics than memorization. So when my preschool-age daughter gets held up on the memorization part, but moves on with little hesitation to the patterns of the twenties and thirties, I feel pretty good about her counting abilities.