I used to practice the times tables with my dad. That’s one of the things we did together. On most nights, when I was little, Dad got home from work after I was already asleep. Sometimes he came into my bedroom anyway and woke me up. I could feel him sitting next to me.

“Hey, Shorty,” he would say.

“Hey, Dad.”

“Sorry to wake you up.” He’d put his hand on my back and give me a tickle under my T-shirt. Sometimes I thought he didn’t really know what to talk to me about. We’d sit like that for a few minutes. Then he’d suddenly say, “Six times eight.”

“Forty-eight.”

“Eleven times twelve.”

“One hundred thirty-two.”

“Fifteen squared.”

“Two twenty-five.”

It made him happy if I got the answers right. Afterward, Dad would push himself up on his knees, sounding tired. “That’s what I do all day,” he liked to say. “Play around with numbers. All right, Son. I think we both need to get some sleep. Good night.”

For the rest of the period, even when we’re talking about other things, I think about the Number Sense competition. I really want to win. With five minutes left, Ms. Kaminski tells us to put our books away. All we need is a pencil and a piece of paper. “I’m going to read out a few questions in a row, and you have to write down the answers as quickly as you can. Without making notes—that’s important. I’ll be walking up and down the aisles just to make sure that nobody cheats.”

My heart has already started beating faster, even though I tell myself, Don’t be silly, this is just a practice test. Nobody cares, it doesn’t matter. My brain has gone blank, but sometimes that’s a good thing—it’s like wiping the blackboard clean before you start.

Ms. Kaminski reads out the first question: 23 times 27. And suddenly I feel happy, because I know the trick—my dad taught it to me. If the tens digits are the same, and the unit numbers add up to ten, there’s a shortcut you can take. You just add one to the first tens digit, and multiply it by the other, then you multiply the unit digits together, and that’s your answer. It sounds complicated, but actually it’s pretty simple. My dad showed me why it works, but I can’t remember the proof. That doesn’t matter because it works anyway, you don’t have to know why. Three times two is six, and three times seven is twenty-one, so the answer is six hundred and twenty-one.

After that, it all seems pretty easy. I just have to stay in the zone. It’s like my brain is better at this stuff than I am, so long as I get out of the way. At the end of the test, Ms. Kaminski goes over the questions one by one. She expects us to call out the answers, but I don’t like showing off. Sometimes I raise my hand, but by that point some other kid has probably beaten me to it. Pete is one of them, he keeps shouting the answers and getting them right, and then I realize that he’s been looking at my paper the whole time and calling out whatever I’ve written down.