The answer for P(A∪B) is 40/45 (or) 8/9.
Explanation:
Given,
The number of students that play only stringed instruments (A) = 35 students.
The number of students that play only brass instruments (B) = 10 students.
The number of students that play both of the instruments = 5 students.
The number of students that play none of the instruments = 5 students.
Probability = Number of required events / Total events
To find the total number of students,
TOTAL = A + B - both + neither.
TOTAL = 35 + 10 - 5 + 5 = 45 students.
P(A∪B) = P(A) + P(B) - P(A∩B)
Probability of A, P(A) = 35 students / 45 students = 35/45
Probability of B, P(B) = 10 students / 45 students = 10/45
Probability of A∩B (both), P(A∩B) = 5 students / 45 students = 5/45
P(A∪B) = (35/45) + (10/45) - (5/45)
= 40/45
P(A∪B) = 8/9