Question

A single letter from the word ADDITIONALLY is chosen. What is the probability of choosing an A or an I? Express your answer as a fraction in lowest terms or a decimal rounded to the nearest millionth.

Answer 1

The probability of choosing an A is:

$P(A)=\frac{2}{12}=\frac{1}{6}$

The probability of choosing an I is:

$P(I)=\frac{2}{12}=\frac{1}{6}$

The probability of choosing an A or an I is the sum of both probabilities:

$P(A\cup I)=\frac{1}{6}+\frac{1}{6}=\frac{2}{6}=\frac{1}{3}$

It means that the answer is 1/3.