SOLUTION: Cindy's job is to check computer printers for defects. Out of 420 printers she has to check, only 3 of the first 84 have been defective. Using this information, what is the best

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Question 161870: Cindy's job is to check computer printers for defects. Out of 420 printers she has to check, only 3 of the first 84 have been defective. Using this information, what is the best prediction of the total number of printers in this group that will be defective?
I know that 420/84 is 5 and that 5x3=15, but how do you set up the problem?
Answer by actuary(112) About Me  (Show Source):
You can put this solution on YOUR website!
3 (defectives found)/ 84 (first printers checked) = total defective (x) / 420 (total number of printers). This is the equation that expresses the proportions Therefore, x = (3*420)/84 (Solving for x)
x = 15