The Missing Digit
The idea: mixing a number's digits and taking away always leaves a multiple of nine.
Read it
Who is in this book
-
Missa A number made by mixing and taking away is a multiple of nine, so its digits add to a multiple of nine from ShowMath -
Marlow Rehearse, perform, then reveal the reason instead of protecting the mystery from ShowMath -
Beto a child of the Green Takes things apart -
Danya a child of the Green Asks "how do we know?"
Every recurring character has a short tune, so you can tell who is on stage before a word is said. The tunes play only when you tap, and the Reading Access sound switch turns them off.
The Honest Page
Which parts of this story are true, stretched or made up?
True
- 7452 take away 4725 is 2727, which is 9 × 303, and its digits add to 18. Every difference in the book is a multiple of nine.
- A number and any mix of its digits leave the same remainder when divided by nine, which is why the old check called 'casting out nines' works. Source
Stretched
- Missa always finds the hidden digit. What we simplified: She can only if the hidden digit is not a 0 or a 9, because those two leave the same sum. That is why the rule says 'not a zero'.
Made up
- The Open Hand troupe and its wagon are made up. Missa and Marlow come from ShowMath.
Tell it back
Tell the story in your own words: who was there, what went wrong, and what they found out. Then the third lock on the troupe's trunk goes on your belt.
On your belt: the third lock on the troupe's trunk.
Your belt lives on this device. Nothing is sent anywhere.
Ring the hammer for someone
Pick this book for someone younger. The link carries only the book, and it will wait for them on the Green.