<PRE><B>Question 702800</B>
Of 10 electric bulbs,three are defective but it not known which are defective. in how many ways can 3 bulbs be selected? 
Ans: 10C3 = 120
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how many of these selections will include at least one defective bulb?
# that have NO defective is 7C3 = 35
# with at least one defective is 120-35 = 85
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Cheers,
Stan H.
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please explain it in step by step when doing the calculation.
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