A 9-sided die has 9 sides meaning that there are a total of 9 possible outcomes.
We are interested in the outcomes "7" OR a "8"
The probability that the number rolled is a "7" is given by
[tex]P=\frac{number\text{ of favorable outcomes}}{\text{total number of outcomes}}[/tex]There is only 1 favorable outcome which is to roll a "7" and the total number of outcomes are 9.
[tex]P(7)=\frac{1}{9}[/tex]So, the probability that the number rolled is a "7" is 1/9
The probability that the number rolled is a "8" is given by
There is only 1 favorable outcome which is to roll a "8" and the total number of outcomes are 9.
[tex]P(8)=\frac{1}{9}[/tex]So, the probability that the number rolled is a "8" is 1/9
The probability that the number rolled is a "7" OR a "8" is given by
[tex]P(7\; or\; 8)=P(7)+P(8)=\frac{1}{9}+\frac{1}{9}=\frac{2}{9}[/tex]There is a 2/9 probability that the number rolled is a "7" OR a "8".