Select the correct answer:

\begin{tabular}{|c|c|c|c|c|}
\hline
Weight & 1000 to 1500 cal & 1500 to 2000 cal & 2000 to 2500 cal & Total \\
\hline
120 lb & 90 & 80 & 10 & 180 \\
\hline
145 lb & 35 & 143 & 25 & 203 \\
\hline
165 lb & 15 & 27 & 75 & 117 \\
\hline
Total & 140 & 250 & 110 & 500 \\
\hline
\end{tabular}

Based on the data in the two-way table, what is the probability that a person weighs 120 pounds, given that he or she consumes 2000 to 2500 calories per day?

A. 0.09
B. 0.12
C. 0.22
D. 0.35



Answer :

To find the probability that a person weighs 120 pounds given that they consume 2000 to 2500 calories per day, we can use the concept of conditional probability. The formula for conditional probability is:

[tex]\[ P(A|B) = \frac{P(A \cap B)}{P(B)} \][/tex]

In this problem:
- [tex]\( A \)[/tex] is the event that a person weighs 120 pounds.
- [tex]\( B \)[/tex] is the event that a person consumes 2000 to 2500 calories per day.

From the given data:
- The total number of people consuming 2000 to 2500 calories per day is 110.
- The number of people who weigh 120 pounds and consume 2000 to 2500 calories per day is 10.

So, the probability that a person weighs 120 pounds given that they consume 2000 to 2500 calories per day is calculated as:

[tex]\[ P(\text{120 lb} | \text{2000 to 2500 cal}) = \frac{\text{Number of people who weigh 120 lb and consume 2000 to 2500 cal}}{\text{Total number of people who consume 2000 to 2500 cal}} \][/tex]

[tex]\[ P(\text{120 lb} | \text{2000 to 2500 cal}) = \frac{10}{110} \][/tex]

Upon simplifying this fraction, we get approximately [tex]\( 0.0909 \)[/tex]. Therefore, the correct answer to the question is:

A. 0.09