Answer :

A recurring decimal is one is which the numbers after the decimal keeps on repeating up till infinity, it does not terminate.

Now for 20/11:      11 into 20 is 1  remainder 9.

20 / 11  = 1 whole number,    9/11.

We can now perform 9/11 with our calculator  = 0.818181.....

The ....... after the 81 signifies it continues in that pattern indefinitely.

Therefore 20/11 =  1 whole number,    9/11= 1 + 0.818181....
                           = 1.818181......
The different digits that appear are 1 and 8.
So 2 different digits appear when 20/11 is written as recurring decimal.