A teacher gave her class two exams; 60% of the class passed the second exam, but only 48% of the class passed both exams. What percent of those who passed the second exam also passed the first exam?

we are given the probility of passing the second exam of 60% and passing the first and second exam equal to 48%. In this case, to determine the percent of those who passed the first exam, we divide 48% by 60% using the rules of probability. The answer should be 80%

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tutisto tutisto · Answer 2 · 2018-07-07T19:31:46+02:00

This is an example of conditional probability because we are trying to find the probability of an event occurring GIVEN the occurrence of some other event. There is a formula for this (see image attached).
If we follow this formula, the numerator would be the probability of (A AND B) which in this case is "48% of the class passed BOTH exams." The denominator in the formula would be that "60% of the class passed ONLY THE SECOND exam."
Therefore, P(A and B) = 0.48, which is 48% expressed as a decimal and P(B)= 0.60, which is 60% expressed as a decimal. Then, you can figure out the answer by dividing.