I am confused by the explanation of OG(11th ed) to Q61 in Data Sufficiency on p282.
How many integers are there between, but not including, integers r and s?
(1) s - r = 10
(2) There are 9 integers between, but not including r + 1 and s + 1.
I understand that (2) is sufficient, but I don't know why (1) is also sufficient.
The question doesn't say anything about whether all integers between r and s are different or whether they can be repeated. If they can be repeated, there can be more than 9 integers within the range of r and s.
Could anyone please help?
We have selected 2 numbers at random r and s and question clearly says integers between, hence the question of repeating does not arise.