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.