### Home > CCG > Chapter 2 > Lesson 2.1.3 > Problem2-35

2-35.

When Ms. Shreve randomly selects a student in her class, she has a $\frac { 1 } { 3 }$ probability of selecting a left-handed student.

1. If her class has $36$ students, how many left-handed students are in Ms. Shreve’s class?

$P\text{(left-handed students) }=\frac{\text{number of left-handed students}}{36}=\frac{1}{3}$

2. If there are $11$ left-handed students in her class, how many students are not left-handed?

$P\text{(left-handed students) }=\frac{11}{x}=\frac{1}{3} \rightarrow x=33$

$\text{# of not left-handed students}=33-11$

3. What is the probability that she will select a student who is not left-handed?

4. Assume that Ms. Shreve’s class has a total of $24$ students. She selected one student (who was left-handed) to attend a field trip and then was told she needed to select one more student to attend. What is the probability that the second randomly selected student will also be left-handed?

Since $\frac{1}{3}\left(24\right)=8$, there are $8$ left-handed students to start out with. However, after $1$ left-handed student is selected, the probability of picking a left-handed student again becomes $\frac{7}{23}$.