Page 60 of Thorne
"Yes. Exactly that. Think of it as every rock has a best friend." I lean closer to the steel slot. "A partner rock that's exactly far enough away to make ten together."
"Nine's best friend is one." The interruption is eager, testing the rule before I can finish explaining it.
"Check it."
I hear her hop the dinosaur. Nine forward one. "Ten. Yes!"
"Eight's is two. Seven's is three."
"Six's is four!" She produces this with the energy of someone staking a claim.
"And five?"
A pause. I hear her work it out.
"Five's best friend is five." The small voice drops, suddenly serious. "Five is its own best friend."
"Yes."
"That's a little sad."
I press my forehead lightly against the cold door. "Or it's self-sufficient."
"What's self-sufficient mean?"
"Complete on its own. Doesn't need a partner to reach ten."
The sneakers stay still.
"I still think it's a little sad," she decides.
We run a few more problems. She rebuilds from zero every time. I catch it on the third problem: the whisper resetting, one, two, three, regardless of how far along the river she already is.
"Lily."
The sneakers still. "What?"
"Your dinosaur is already on seven. He doesn't need to swim back to zero and start over. He just starts hopping from where he is."
A long pause. I can almost hear her reconsidering six years of arithmetic from scratch.
"Eight." A cautious pause, and then: "Nine. Ten. Eleven."
Silence.
"That was faster." Her voice has an edge in it: not quite indignant, not quite something else. "Why didn't anyone tell me that?"
"I don't know."
"That's a bad system."
"Yes," I say. "It is."
She works through two more, the whisper starting mid-river now, the dinosaur landing right where he left off. Each answer arrives correctly, and she knows it's correct, the particular quality of certainty that doesn't need me to confirm it.
She's quiet for a moment, shuffling the papers on her side of the slot.
"Is there a faster way than hopping one rock at a time?" The curiosity is palpable through the gap.
