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In a math class with 19 students, a test was given the same day that an assignment was due. There were 12 students who passed the test and 13 students who completed the assignment. There were 4 students who failed the test and also did not complete the assignment. What is the probability that a student who completed the assignment passed the test?
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In a math class with 1919 students, a test was given the same day that an assignment was due. There were 1212 students who passed the test and 1313 students who completed the assignment. There were 44 students who failed the test and also did not complete the assignment. What is the probability that a student who completed the assignment passed the test?\newlineAnswer:

Full solution

Q. In a math class with 1919 students, a test was given the same day that an assignment was due. There were 1212 students who passed the test and 1313 students who completed the assignment. There were 44 students who failed the test and also did not complete the assignment. What is the probability that a student who completed the assignment passed the test?\newlineAnswer:
  1. Total Students Count: First, let's determine the total number of students who either passed the test or completed the assignment, or both. We know that 44 students neither passed the test nor completed the assignment. Since there are 1919 students in total, this means that 194=1519 - 4 = 15 students either passed the test, completed the assignment, or did both.
  2. Find Students Both Passed and Completed: Next, we need to find out how many students both passed the test and completed the assignment. We can use the principle of inclusion-exclusion for this. The formula is:\newlineNumber who did both =(Number who passed the test)+(Number who completed the assignment)(Total number who passed the test or completed the assignment or both)= (\text{Number who passed the test}) + (\text{Number who completed the assignment}) - (\text{Total number who passed the test or completed the assignment or both})
  3. Calculate Number Who Did Both: Now we plug in the numbers we have:\newlineNumber who did both =12+1315= 12 + 13 - 15
  4. Calculate Probability: Calculating the number who did both gives us:\newlineNumber who did both = 251525 - 15\newlineNumber who did both = 1010\newlineSo, there are 1010 students who both passed the test and completed the assignment.
  5. Calculate Probability: The probability that a student who completed the assignment passed the test is the number of students who did both divided by the number of students who completed the assignment.\newlineProbability = Number who did bothNumber who completed the assignment\frac{\text{Number who did both}}{\text{Number who completed the assignment}}
  6. Final Probability: Plugging in the numbers we have:\newlineProbability = 1013\frac{10}{13}
  7. Final Probability: Plugging in the numbers we have:\newlineProbability = 1013\frac{10}{13}The fraction 1013\frac{10}{13} cannot be simplified further, so this is the final probability.

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