Question

The probabilities that a student will solve Question A and Question B are $0.4$ and $0.5$ respectively. What is the probability that he solves at least one of the two questions?

• A. $0.6$
• B. $0.7$
• C. $0.8$
• D. $0.9$

Answer 1

The correct option is B $0.7$

Given probabilities that a student will solve Question A and Question B are $0.4$ and $0.5$ respectively

Probability the student will not solve any are $1-0.4=-0.6$ and $1-0.5=0.5$ respectively

and

probability that he solves at least one of the two questions

$\Rightarrow \left(totalprobability\right)-\left(\text{not solved at least one}\right)=1-(0.6\times 0.5)=1-0.3=0.7$

Therefore, Answer is $B$