Math Is Fun Forum

oh,sorry i think i misread the problem.i thought it said edge

hi juantheron

i got 1/18.

hi juantheron

i will try to do this:
let's say we pick a random 3-digit number abc

if it is divisible by 11 then (a+c)-b must be divisible by 11 as well,so a+c=b or a+c=b+11

now if abc is divisible by 9 then a+b+c is divisible by 9 as well.

so: a+b+c=9k
(a+c)+b=9k
b+b=9k or b+11+b=9k

in the case where 2b=9k we see that b is either 0 or 9 which means that a+c is 0 or 9.because a cannot be zero a+c cannot be zero which leaves the case a+c=9 and b=9.so for this case we have 9 numbers.

in the case where 2b=9k-11:

notice that b is in the interval [0,9]

so 2b is in the interval [0,18]

so 2b+11 is in the interval [11,29]

and numbers divisible by 9 from this interval are possibilities for k,and those are 18 and 27.

a) if k=18 then
2b+11=18
2b=7
impossible because b is a natural number (a digit).

b) if k=27
2b+11=27
2b=16
b=8

now:
a+c=b+11
a+c=19

no two digits satisfy this equation.

so by analyzing all the cases we get that a+b=9 and b=9.

So the possibilities for the number abc are:
198,297,396,495,594,693,792,891,990

now we just calculate the number of 3 digit numbers divisible by 11 (which is floor(1000/11))

thanks bob

ok bobbym i'll let you off with a warning,but if this happens again i will not be so tolerant

no it wasn't,it was you.

don't lie to me i saw the whole thing.you with a miniature hammer in your hand,a snail just begging not to be hit,and you slamming it.

i would give them an irrational number so they would never find it...or to be sure i would give them an octonion

hi MIF

yes that is very practical especially for students that have a focus on algebra.

another thing.sometimes when i zoom in i go to far to the left and when i press the zero button it centers it but it also resets the zoom. it would be nice to have separate buttons for centering the number line at 0 and for resetting the zoom.

one more idea.you could add a place to type in a number and it finds it instantly(well,maybe not instantly) on the line,so that e.g. i don't have to have my arm fall off just to reach 154.7

snails can defend themselves.they are not as helpless as you think.they have their miniature swords.speaking of snails i should change my avatar!

ok,so you are a 10 year old warrior who likes to torture snails??? you are unbelievable,you are my idol!!!

I LOVE BOBBYM!!! I LOVE BOBBYM!!! I LOVE BOBBYM!!!

even our national news reporters have to say 'I love bobbym' every 10 seconds.

didn't you already take over the world? my whole town is wearing "I <3 bobbym" t-shirts!