Question

There are four racks numbered 1, 2, 3, 4 and four books numbered 1, 2, 3, 4. If an even rack has to contain an odd-numbered book and an odd rack contains an even-numbered book, then what is the position of book 4?
[I.] Second book has been put in third rack.
[II.] Third book has been put in second rack.

• A. if the question can be answered with the help of any one statement alone but not by the other statement.
• B. if the question can be answered with the help of either of the statements taken individually.
• C. if the question can be answered with the help of both statements together.
• D. if the question cannot be answered even with the help of both statements together.

Hint:

Apply the parity condition (odd-even matching) and test each statement logically.

Answer 1

The Correct Option is A

Using Statement I, if the second book is in the third rack, we can use the rule: - Even rack → odd-numbered book - Odd rack → even-numbered book Rack 3 is odd, and Book 2 is even, so this is valid. Using this clue, one can deduce the rest of the configuration. Statement II is just the reverse and does not help uniquely.