A teacher gave his class two quizzes; 80% of the class passed the first quiz, but only 60% of the class passed both quizzes. What percent of those who passed the first quiz also passed the second quiz?
@mathmale

Question

A teacher gave his class two quizzes; 80% of the class passed the first quiz, but only 60% of the class passed both quizzes. What percent of those who passed the first quiz also passed the second quiz?
@mathmale

mathmale · Answer

Is this the problem to which you were referring?

anonymous · Answer

yes.

anonymous · Answer

Or it might not be it could also be this
60/80 = 75%

anonymous · Answer

The answer is 75% I'm sure of it.....I think.

mathmale · Answer

So your textbook or the computer tells you that the answer is 20%  I doubt that.  I'd vote for your second try:  60/80 = 75%.  75% of those who passed the first test also passed the second.   Sounds right to me.