“Prime Climb Success Story”

March 9, 2022
I recently received this lovely email entitled Prime Climb Success Story. The thinking here is super interesting, in my opinion, and wonderfully idiosyncratic. Can you figure out what the 10-year-old is doing?

Hello,

I was driving and my 5 year old asked out of nowhere, what’s 16 times 16?

My 10 year old said, “I can figure that out. 10 times 16 is 160. Add 8 times 10, that’s 80, to get 240. Add 8 times 2, that’s 16, and the total is 256.”
My husband, a professor of astrophysics at a top-10 university, and I could not figure out what he was doing to get the right answer. We play Prime Climb with him regularly, though, so it had to do something with manipulating factors.
After taking care of the 10s place to get the 160 part (16×10), he still had to compute 16 times 6. To do that, he reformatted it as (8×2) x (5+1). Then distributing, we have for the first part (8x2x5) = 8×10, which is 80; for the second part (8×2)x1, which is 16.
I sat him down and asked to diagram that method, supplemented with a diagram. Attached is how he had reformatted the problem to reach the “gole.” Given what he actually wrote, it’s clear he’s more comfortable with 5s and 10s than anything else. Having computed 16×10, he knew he could get 16×5 by taking half-again. Then he was left with one more 16 to get to the final answer.
P.S. When is Spelling Climb coming out?

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