How to calculate the odds of this

How to calculate the odds of this

random number between 0 and 1000

if the random number is = or greater then 900 or = or less then 100, then you win.

How would I go about calculating the odds of that percent wise?

P (# >= 900) = 101/1001 (including 1000)
P2 (# <= 100) = 101/1001 (including 0)

P3 (P + P2) = 202/1001
202/1001 = .2017 or 20.17%

Well, you have a range of 1,000 possibilities, and you are only excepting the numbers 900-1000 or 0-100 which gives you 200 numbers. That means 200 out of 1000 will win, which reduced is 1/5 or 20% (1 divided by 5= 0.2 which when the decimal is moved twice to the right, is 20%)

100 numbers between 900 and 1000, 100 numbers between 0 and 100. That's

200 in 1000 chance, or 1 in 5, or 20%

1 in 5 or 20%