Question

Students A and B have probabilities of failing an exam of $1/2$ and $1/5$ respectively. The probability of them both failing the examination is $1/10$. Determine the probability that at least one of the two students fail.

• A. $0.5$
• B. $0.6$
• C. $0.7$
• D. $0.8$

Answer 1

The correct option is B $0.6$

Students A and B have probabilities of failing an exam of $\frac{1}{2}$ and $\frac{1}{5}$ respectively. The probability of them both failing the examination is $\frac{1}{10}$

$P(A\cup B)=P\left(A\right)+P\left(B\right)-P(A\cap B)=$$\frac{1}{2}$$+\frac{1}{5}$$-\frac{1}{10}$$=\frac{6}{10}=0.6$