Question

Let A and B be two events such that $P\left(A\right)=0.3$ and $P(A\cup B)=0.8$ if A and B are independent events, find $7P\left(B\right)$

• A. $5$
• B. $4$
• C. $1$
• D. $3$

Answer 1

The correct option is A $5$

As A and B are independent

$0.8=P(A\cup B)=P\left(A\right)+P\left(B\right)-P\left(A\right)P\left(B\right)$

$=0.3+P\left(B\right)-\left(0.3\right)P\left(B\right)$

$\Rightarrow 0.5=\left(0.7\right)P\left(B\right)$

$\Rightarrow 7P\left(B\right)=5$.