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A box contains 5 detective and 15 non-detective bulbs. Two bulbs are chosen at random. Find the probability that both the bulbs are non-defective.

5/19
3/20
21/38
None of these

Correct Answer: 21/38

Explanation:

n(S) = $C 220$ = 190

n(E) = $C 215$ = 105

Therefore, P(E) = 105/190 = 21/38

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