the table below gives the probability density of grades for a particular class.\ngrade a b c d…

the table below gives the probability density of grades for a particular class.\ngrade a b c d f\nprobability 0.22 0.29 0.27 0.15 0.07\nif a student is selected at random, what is the probability that their grade is a c or d?\np = ?

the table below gives the probability density of grades for a particular class.\ngrade a b c d f\nprobability 0.22 0.29 0.27 0.15 0.07\nif a student is selected at random, what is the probability that their grade is a c or d?\np = ?

Answer

Explanation:

Step1: Identify relevant probabilities

The probability of grade C is $0.27$ and of grade D is $0.15$.

Step2: Use addition rule for mutually - exclusive events

For mutually - exclusive events, the probability of event A or event B is $P(A\cup B)=P(A)+P(B)$. Here, the events of getting a C and getting a D are mutually - exclusive. So $P(C\cup D)=P(C)+P(D)$. $P(C\cup D)=0.27 + 0.15$ $P(C\cup D)=0.42$

Answer:

$0.42$