## Saturday, September 26, 2009

### Back to School Night's Puzzle #2

Here is another puzzle that was presented to us, parents, at the back to school night.

Find the In-Out pattern and complete the missing Out numbers:

In - Out
1 - 1
6 - 6
13 - 4
45 - 9
78 - 6
91 - 1
87 - ?
101 - ?
7 - ?

Submit your answer on our Family Puzzle Marathon site. Solve three puzzles and get a prize!

Barry said...

I found a pattern, but it's probably more complicated than what you had in mind. Take each "in" number and add the digits together. Then, take the result and add those numbers together. So, for example, 78 -> 7+8 -> 15 -> 1+5 -> 6
So for the last three numbers:
87 -> 8+7 -> 15 -> 1+5 -> 6
101 -> 1+0+1 -> 2
7->7

Maria said...

Barry, you are absolutely right!

This is the technique that my son's teacher called "code answer". You can code multi-digit number into a single digit. Obviously, this only works one way and you couldn't recover the original number: 19 and 91 both give 1 as 1+9=10, then add 1+0=1
However kids could use these "code answers" to verify the addition that they do:

71 + 26= 97
replace numbers with their corresponding "code numbers" and addition should still work:
8 + 8 = 16 (7 in code)