What is the probability that a randomly selected three-digit number is divisible by 11? Express your answer as a common fraction.
We need to figure out the denominator first of the probability fraction
100-999
That is 900 digits
Ok so our denominator is 900
Now we need to figure out the numerator. We do this by finding all the three digit numbers divisible by 11
We try listing (I couldn't find any better way to do this
110
121
132
143
154
165
176
187
198
----
209
220
231
242
253
264
275
286
297
----
Notice how the first number's last two digits start from 10 then decreases to 9 at 200
notice how the last number last two digits start from 98 and decrease to 97 at 200
This means each hundred we have 9 numbers divisible by 11
This means that there are 9*9 (9 different hundreds) = 81 numbers
We have the numerator which is 81 and the denominator which is 900
Simplifying we have \(\boxed{\frac{9}{100}}\)