If you add the two digits of your age, what number do you get?
Asked by
josie (
30934
)
March 23rd, 2019
Assuming you have to be at least 13, and you are not 100 or over.
If you are 100 or over, just clarify that and add all three.
Observing members:
0
Composing members:
0
32 Answers
Will you be computing our ages from the answers?
9. Same as Nine years ago, and nine years before that, and nine years from now.
^^ Exactly. If I can guess your decade, I know your age. Let’s say you answer “2” and I know you’re in your forties. Ergo, you’re 47.
But 4 plus 7 equals 11. Or did I misunderstand?
@joeschmo
Yes friend, 4 plus 7 does equal 11.
I keep forgetting that Fluther is a difficult crowd. I should have learned on my bracket question. No way to keep it simple here.
I don’t care how old your are.
If the number is 12, you could be 66, or 48, or 39. Etc.
Keep adding until you’re down to one digit. 4 + 7 = 11, 1 + 1 = 2.
“Casting out nines” is a trick I learned in about seventh grade. It’s a great way to check your arithmetic quickly. You add the digits together and keep adding them until you’re down to one, treating a 9 as zero. Then when you perform the computation, the answers should match. For example:
681 = 15 = 6 +
235 = 10 = 1
__________
916 = 7
If the actual total doesn’t reduce to a number that matches the 9less total, there’s a mistake in your arithmetic. It works for addition, subtraction, multiplication, and division.
So—using whatever answer you get when you’ve added the digits of your age together, and kept adding until you’re down to one digit, your age is going to be a multiple of 9 plus whatever your answer was.
If your answer is 2, then you’re 11, or 20, or 29, or 38, or 47, and so on. So…if I can guess your decade, I know your age.
She is, quite brilliant.
I shall not reveal my digits then. Let’s say I’m 12.
@Jeruba That’s also a quick way to see if any number is divisible by 3. In your example, 681 is divisible by 3. 235 is not.
2 + 7 = 9
At least it did last time I checked.
I love that expression, casting out nines. When Adam and Eve left Eden, the nines were forced to join them.
Apropos of nothing, here is a math trick that uses casting out nines. Write down a number several digits long. Form a second number by scrambling the digits of the number. Subtract the smaller from the larger and cast out nines on the answer. I put a spell on you forcing the final number to be nine.
@josie You got that right fella, I myself read no more into your question than as if it were a song from Sesame Street.
Oh, that’s not my trick. I learned it from my seventh grade math teacher, Miss Taylor. Over the years I’ve used it many times to check my arithmetic because I’m not very good at it, even in simple problems like computing my checkbook balance. I just wondered if @josie was getting ready to pull a rabbit out of a hat by correctly guessing people’s ages.
Gosh, I haven’t entered my purchases in in checking register in AGES! I almost never write checks any more, for one thing.
9, and I’m not 18, 27, 36, 45, 54, 63, 81, 90, or 108.
Give up?
¡ǝǝɹʇ ɐɾuᴉu ʇuɐʇnɯ oʎ 90Ɛ ɐ ɯ,I
72. Plus the year of your birth is part of your screen name, and you haven’t had your birthday yet this year!
Wow, if your digits add up to 72, I won’t even try to guess your age! ;-o
I think so far I’m the “youngest” number, so I get to ask the questions at dinner.
That was short lived. I have been unseated.
Given the longest known lifespan of a human being, the highest total anyone can have is 18.
If only math (without any reasonable empirical limitations) is considered, the oldest someone can be with a total of 1 is 1 followed by an endless string of zeros.
Answer this question 
