Mean or Expected Value and Standard Deviation · Exercise 9

A physics professor wants to know what percent of physics majors will spend the next several years doing post-graduate research. They have the following probability distribution.
$$\begin{array}{ccc}\text{x}& \text{P(x)}& \text{x*P(x)}\\ \text{1}& \text{0.35}& \\ \text{2}& \text{0.20}& \\ \text{3}& \text{0.15}& \\ \text{4}& & \\ \text{5}& \text{0.10}& \\ \text{6}& \text{0.05}& \end{array}$$

FInd the probability that a physics major will do post-graduate research for at most three years. P(x ≤ 3) = _______

This exercise has fill-in blanks from its source book and no answer key.

OpenStax, Introductory Statistics 2e · §4.2 Mean or Expected Value and Standard Deviation · Exercise 9