Find the missing probability.

[tex]\[ P(A)=\frac{7}{20}, \; P(B)=\frac{3}{5}, \; P(A \cap B)=\frac{21}{100}, \; P(A \cup B)=\;? \][/tex]

A. [tex]\(\frac{7}{50}\)[/tex]
B. [tex]\(\frac{91}{400}\)[/tex]
C. [tex]\(\frac{301}{400}\)[/tex]
D. [tex]\(\frac{37}{50}\)[/tex]



Answer :

To find the missing probability, [tex]\( P(A \cup B) \)[/tex], we use the formula for the union of two events. The formula is:

[tex]\[ P(A \cup B) = P(A) + P(B) - P(A \cap B) \][/tex]

Given the probabilities:

[tex]\[ P(A) = \frac{7}{20} \][/tex]
[tex]\[ P(B) = \frac{3}{5} \][/tex]
[tex]\[ P(A \cap B) = \frac{21}{100} \][/tex]

Let's find the numerical values of these probabilities:

1. Converting the given fraction to a decimal, we find [tex]\( P(A) \)[/tex]:

[tex]\[ P(A) = \frac{7}{20} = 0.35 \][/tex]

2. Converting the given fraction to a decimal, we find [tex]\( P(B) \)[/tex]:

[tex]\[ P(B) = \frac{3}{5} = 0.60 \][/tex]

3. Converting the given fraction to a decimal, we find [tex]\( P(A \cap B) \)[/tex]:

[tex]\[ P(A \cap B) = \frac{21}{100} = 0.21 \][/tex]

Now, substitute these values into the formula:

[tex]\[ P(A \cup B) = 0.35 + 0.60 - 0.21 \][/tex]

Performing the addition and subtraction:

[tex]\[ P(A \cup B) = 0.95 - 0.21 = 0.74 \][/tex]

Convert the decimal result back to a fraction. Recall that:

[tex]\[ 0.74 = \frac{74}{100} = \frac{37}{50} \][/tex]

Thus, the missing probability is:

[tex]\[ P(A \cup B) = \frac{37}{50} \][/tex]

So, the correct answer is:
[tex]\[ D. \frac{37}{50} \][/tex]