### Home > INT2 > Chapter 4 > Lesson 4.2.3 > Problem4-87

4-87.

​Refrigerators that are produced on an assembly line sometimes contain defects. The probability that a refrigerator has a paint blemish is $4\%$. The probability that it has a dent is $\frac{1}{2}\%$. The probability that it has both a paint blemish and a dent is also $\frac{1}{2}\%$. What is the probability that a refrigerator has a paint blemish or a dent? What can you conclude about defects on these refrigerators?

$P(A\text{ or }B)=P(A)+P(B)−P(A\text{ and }B)$

$P(\text{Blemish or Dent})=P(\text{Blemish})+P(\text{Dent})−P(\text{Blemish and Dent})$

$P(\text{Blemish or Dent}) = 4\% + 0.5\% − 0.5\%$
$P(\text{Blemish or Dent}) = 4\%$

Conclusion: If a refrigerator has a dent, it also always has a paint blemish.