The odds that an american is of english ancestry are 1: 9. what is the probability that an american is of english ancestry?

There are 36 possible outcomes of the additive dice roll. The way to roll a sum of 9 is 6 (and vice versa) and 3 or 5 and 4 (and vice versa). This is possible 4 of the 36 times, giving a probability the sum of the two dice rolled of 4/36 or 1/9.

If the odds are 1:9 than the probability is:
1 - 1/9 = 8/9 
100 / 9 * 1 = 11.111.. ⇒ 11.11 %

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