Question

The chances to fail in Physics are $20\%$ and the chances to fail in Mathematics are $10\%$. What are the chances to fail in at least one subject?

• A. $28\%$
• B. $38\%$
• C. $72\%$
• D. $82\%$

Answer 1

The correct option is A $28\%$

Let $P\left(A\right)=\frac{20}{100}=\frac{1}{5},P\left(B\right)=\frac{10}{100}=\frac{1}{10}$

Since, event are independent and we have to find $P(A\cup B)=P\left(A\right)+P\left(B\right)-P\left(A\right)\cdot P\left(B\right)$

$=\frac{1}{5}+\frac{1}{10}-\frac{1}{5}\cdot \frac{1}{10}$

$=\frac{3}{10}-\frac{1}{50}=\frac{14}{50}=\frac{14}{50}\times 100=28$%