One or more options correct
A number is chosen at random from . Let , , be the events that the number is divisible by , by and by respectively. Which of the following is (are) correct?
- A. and are independent events
- B. and are independent events
- C.
- D. The events , , are pairwise independent
Show answer and solution
Answer: A
Counting in : , , , so , , . The number is in exactly when it is a multiple of , so , and are independent (A true). Every multiple of is even, so and , whereas ; hence are not independent (B false). Because , and (C false). Pairwise independence would need all three pairs to be independent, but the pair fails, so D is false (note are independent since multiples of number ). Only the statement in option A is correct; a brute-force enumeration over the sixty outcomes confirms each count.
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