X and Y are two events. The probability of X or Y is 0.7 and that of X is 0.4. If X and Y are independent, find the probability of Y.
A
0.30
B
0.50
C
0.57
D
1.80
Verified Correct Answer: A.
Step-by-Step Mathematical Solution
P (X or Y) = P(X) + P(Y), when they are independent as given.
0.7 = 0.4 + P(Y)
P(Y) = 0.7 - 0.4 = 0.30
Source: Myschool Past Questions Archive (Record #926)