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A quality control inspector is checking a
sample of light bulbs. The table summarizes
her results. If one of the light bulbs is selected
at random, find the probability that the light
bulb is defective, given that it is a 20 or 100
watt bulb.
Wattage Good Defective Total
20 90. 5. 95
50. 73. 5. 78
100. 89. 8. 97
Total 252 18. 270
The probability is
(Simply)
