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Question
A box contains 100 bulbs, 20 of which are defective. 10 bulbs are selected for inspection. Find the probability that: all 10 are defective
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Solution
Out of 100 bulbs, 10 can be chosen in 100C10 ways.
So, total number of elementary events = 100C10
There are 20 defective and 80 non-defective bulbs.
The number of ways of selecting 10 defective bulbs out of 20 is 20C10 ways.
∴ Favourable number of elementary events = 20C10 ways
Hence, required probability = \[\frac{^{20}{}{C}_{10}}{^{100}{}{C}_{10}}\]
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