Page 63 of Thorne

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"Is that flying?"

"Close."

She slides new paper through. A fresh sheet, no eraser damage. She's conserving her resources.

"I want a trick." Her small, demanding voice carries a touch of stubbornness.

"Which one?"

"For five."

I consider how to land this for a six-year-old. "What's ten times three?"

"Thirty." The answer is hesitant, trailing off into the quiet hall. "Is that right?"

"Yes. You add a zero. The dinosaur takes one enormous jump, ten rocks at once."

"Okay." More confident now.

"Five is exactly half of ten." I tap the concrete floor. "So five times any number is ten times that number, then cut in half."

A pause.

"Five times three," I prompt. "Ten times three is thirty. Cut in half."

I hear her working. "Fifteen."

"Yes."

"Five times six. Ten times six is sixty. Half of sixty …" A longer pause. She's feeling out sixty, halving it on the rocks. "Thirty."

"Yes."

"Five times seven. Ten times seven is seventy. Half of seventy …" The pause stretches. This is the harder one, odd numbers that won't split clean. "I can't cut seventy in half. It goes weird."

"Seventy is sixty plus ten," I say. "Half of sixty is thirty. Half of ten is five."

A silence. Then: "Thirty-five."

"Yes."

Another silence, longer.

"Five is ten's little sister." I hear her shifting on the floor outside.

I look at the ceiling.

"Yes," I say. "Exactly."

She works through every number she can think of. Five times two, five times four, five times nine. Each time she finds theten-times first and halves it, the process clean and certain, the dinosaur taking the big jump and then coming back halfway.

"All the fives end in zero or five." The discovery is offered proudly after the seventh problem.

"Yes."

"That's because ten's little sister can only land on ten-rocks or half-rocks."

I have nothing to add to this. "Yes." I lean closer to the door. "That's exactly why."

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