Answer:
a) The expected number of questions that are answered correctly by both A and B = 11 (7 + 4).
b) The Variance of the number of questions that are answered correctly by either A or B = 2.25.
Step-by-step explanation:
Number of questions in the examination = 10
Probability of A's answer being correct = 0.7
Probability of B's answer being correct = 0.4
The expected number of questions that are answered correctly by both A and B:
Probability of Expected
Correct Answer Value Variance
A 0.7 7 (0.7 * 10) 2.25
B 0.4 4 (0.4 * 10) 2.25
Total expected value = 11
Mean = 5.5 2.25
