Suppose A and B are two events with P(A)=0.5 and P(A∪B)=0.8. Let P(B)=p if A and B are mutually  exclusive and P(B)=q if A and B are independent events  then the value of q/p is

When A and B are mutually exclusive, P(A∩B)=0∴    P(A∪B)=P(A)+P(B)----1⇒    0.8=0.5+p⇒    p=0.3    P(A∪B)=P(A)+P(B)----2    =P(A)+P(B)−P(A∩B)    =P(A)+P(B)−P(A)P(B)⇒    0.8=0.5+q−(0.5)q⇒    0.3=q2⇒    q=0.6-----3⇒    q/p=2