Answer:
- P (blue or too big) = 11 / 12
Explanation:
A two way table permits to represent the situation clearly and find the answser is an easy way.
The two way table is that results from the given information is:
Initial information:
Blue Green Total
Fit well 4 1 ?
Too big ? ? ?
Total 5 7 12
Now by subtraction and addition you can fill the unknown fields:
Blue Green Total
Fit well 4 1 5
Too big 1 6 7
Total 5 7 12
Now, you can see that there are 5 blue and 7 too big shirts, but the total number of them is 5 + 7 - 1 (because one of the too big shirts is also blue).
Then, the number of shirts being blue or too big is 5 + 7 - 1 = 11.
And the probability is :
- P(blue or too big) = number of blue or too big / total number of shirts
- P (blue or too big) = 11 / 12 ← answer
You can also realize that there is only 1 green shirt that fits well, and that is the only option of not being blue of too big, so 1 /12 is the probability of not being blue or too big, and its complement (being blue or too big) is 1 - 1/12 = 11 / 12.
