Question

A box contains 20 defective items and 80 non-defective items. If two items are selected at random without replacement, what will be the probability that both items are defective.?

1. \(\frac{1}{5}\)
2. \(\frac{1}{{25}}\)
3. \(\frac{{20}}{{99}}\)
4. \(\frac{{19}}{{495}}\)

Answer 1

Correct Answer - Option 4 : \(\frac{{19}}{{495}}\)

Total number of items = 100

Number of defective items = 20

Number of Non-defective items = 80

Then the probability that both items are defective, when 2 items are selected at random is,

 \(⇒P=(20C_2×80C_0)/(100C_2 )=19/495\)