999

ETan

Golden Member
PROBLEM.

The number 11 can be represented using exactly three 9's as 11=99/9.

Amazingly, the number 20 can also be expressed using exactly three 9's and elementary arithmetic signs.

What is this expression?

azztec

99/9+9=....20

Diamond Member
that's not exactly three 9s, but it does work

azztec

Senior member
oops, my brain didnt want me to read the part about 3 nines

polotek147

Platinum Member
What class is that for? Seems like a cool class, really makes you pick your brain out.

arcain

Senior member
9+9+sqrt(9) = 18+3 = 21

Doh.. thought that said 21! <slaps forehead>

hrmm.. must be time to go to sleep.

AgentofEvil

Senior member
EDIT
Hey, wait that's wrong.

azztec

Senior member
at least mine added up to 20

polotek147

Platinum Member
So, you only have to use 9's, or can you use other #'s too? Don't mind me, my brained is pretty fried right now from the late night coding.

ETan

Golden Member
guess i'm not the only that's stumped by this question. It's actually part of a "Problem of the Week" that the math dept hosts. I like the idea. Prize kinda sucks though... at the end of semester, winner gets \$20. Not great, but it's fun, and rewarding if u win. Or loose.

AFAIK only 3 9's are allowed, no other numbers. I pretty much picked the whole thing apart yet still no answer.

Wish i could use 4 9's...

serialb

Diamond Member
<<at the end of semester, winner gets \$20. Not great, but it's fun, and rewarding if u win. Or loose>>

Aren't you cheating now?

serialb

Flip 999 around 180 degrees.
You get 666.

(9+9)/.9 = 20

johneetrash

Diamond Member

<< (9+9)/.9 = 20 >>

good stuff

But .9 isn't 9

1 + 1 = 2

thereds

Diamond Member

<< 1 + 1 = 2 >>

I forsee you working at NASA.

Oalex

Senior member

<< But .9 isn't 9 >>

is a decimal point an elementary arithmetic sign?