15.2.41 One dimensional random variables and their characteristics

Problem: The student answers three questions on the examination card. The probability of a correct answer to the first question is equal to 0,5 , to the second one is 0,7 and to the third question 0,9 . It is required: a) make a distribution series of the number \( X \) of the questions, which are given correct answers; b) find the expected value and the dispersion of the random variable \( X \); c) accurately plot the graph of its function of the distribution \( F_{X}(x) \).