How can you quickly check whether a number is exactly divisible by 9?

Correct answer: If the sum of its digits is exactly divisible by 9

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What people think about it: 15 Comments
tinabobina
tinabobina
9, 18, 27, 36, 45, 63, 72, 81, 90... notice the digits add to 9 (at least up 9 x 10).
Centenarian
Centenarian
Understanding mathematics is the key to unlocking the secrets of the universe
* Seshati *
* Seshati *
tinabobina, thanks for the life of me I was kinda finding the blurb a wee bit hard to understand lol! With your addition it’s a face palm moment haha 😆
GruffSecretAgent9936
GruffSecretAgent9936
It also works for 3.
Player #3833664
Player #3833664
@tinabobina, Thanks for examples dat was lacking in the blurb
Republic of Taiwan
Republic of Taiwan
This sounds like a level 1 question
Player #33292972
Player #33292972
tinabobina, I never took notice of that, boy it’s true you learn something new every day
Lash
Lash
GruffSecretAgent9936, they never told me about 3...only 9! thanks 😊
Chris
Chris
tinabobina, In 77yrs I never noticed that...how clever and a very interesting fact.
thom
thom
this doesn't help me in the mini game.
Milo
Milo
Dī-oh-nī’-sus, best joker în this game...
Aradlaw
Aradlaw
noooo, not starting math questions!
SOOTI
SOOTI
That answer would have been easier if 'all the digits add to 9' had been an option.
luckycatfay
luckycatfay
TQOP24, nothing to do with maths but when I play games on my phone it burns my fingers after a while is this common?
Player #3833664
Player #3833664
@tinabobina, examplez does look like the 9 times table