FORWARD.

FOUR + WORD – U + Replace second ‘O’ with ‘A’ => FORWARD

(‘FORE’ also can take the place of ‘FOUR’)

The tank / other place where the drainage ends. (The more you shower, the more dirt will go down the drain and accumulate in the tank, making it dirtier.)

1. Whose birthday does not come every year? — Someone who was born on 29th February.
2. Which is the fruit that does not sell even after being sweet? — a rotten fruit (nobody would buy it, however sweet it may be)
3. What is the thing that breaks down on speaking? — Silence
4. What does not dry in the sun? — ice 
5. What is it that runs without feet and does not return? — water (stream / river)
6. Which fish cannot swim in the ocean? — A fish that’s DEAD…! (It can’t swim anywhere!) OR a fish that lives anywhere outside the ocean (e.g. in a river / pond / aquarium) – It can’t swim in the ocean unless it is put in the ocean first!

The ‘expected’ answer is that,
If the man had indeed thought that it was his room as he claimed, he wouldn’t have knocked, but tried to open the door straight away because he should be having the key with him, and hence, he lied, making the woman suspicious about his motive and tempting her to call security.

My answer (posted under the original puzzle post above):
The man’s explanation – that he thought it was his room – sounds suspicious, but the statement in itself need not necessarily be a reason for raising an alarm, because the statement could be true. (Consider the situation wherein the man had gone out leaving his wife / someone else in the room. Then he needn’t have the key with him. He comes back and knocks the wrong door by mistake.) A better reason for suspicion is that after giving his ‘explanation’,he walked to the elevator (to go to a different floor, may be.) It seems less likely that he might go to the wrong floor AND wrong room. (Of course, even that is not outright impossible.)

You are a MESSAGE (even though I may not read you ‘daily’)

5, 6, 7 => AGE (increase every year)
3, 4 => ‘S’ (same)
3, 2, 5 => SEA (covers 79% of the world)

The question, when taken in the exact sense, has no solution because the sum of three ODD numbers can never be an EVEN number, whether 30 or 300, whereas all the numbers in the list given are odd.

However, since this is indicated as a ‘Tricky puzzle’, it means that there should be some ‘tricky’ way to solve it. So, here we go:

Since the puzzle specifies no rule / condition that prohibits use of mathematical operators, we could use the ‘factorial’. So,
(3!) + (11) + (13)  = 6 + 11 + 13 = 30

(Other options may also be possible.)

Assuming that Harry & friends don’t have to bother about food for return journey: (As stated in the puzzle, they are planning to go to the island only, and not to return!),  just two friends would be sufficient.

Day 0: At the time of leaving, all three (Harry and two friends) will carry 4 days’ provisions each.
Day 1 End of day: All three will have three days’ food left. Now, friend 1 will return, taking one day’s food (required for the return trip), leaving 2 days’ food with Harry & the second friend. Harry & Friend 2 continue the journey, both of them now with 4 days’ food each. (3 days’ food they themselves had carried plus the two days’ food left by Friend 1, divided among them.)
Day 2 EoD: Both have 3 day’s food left again. Friend 2 returns taking two days’ food, leaving one day’s food with Harry. Now, Harry has sufficient food for 4 days (3 days’ food he had carried and one day’s food left by the friend).
Days 3 – 6: Harry can complete the remaining journey (4 days) with that food. Mission Accomplished.

I Understand (the puzzle!) 🙂

Even though this question is marked “answered”, I would say that it is ‘faulty’ on TWO counts, especially looking at the accepted ‘best answer’.

1. The question says “From the bedroom his wife shouts “Hi sweetie, could you have a look at the microwave and tell me how much time is left?” and “He immediately runs out and calls the police“. It is nowhere stated that the husband actually looked at the microwave, whereas the “Best answer” assumes that he did and saw the time left is 9:11, prompting him to dial the Emergency. If it is acceptable to assume that the husband checked the microwave (even though the question doesn’t mention it), it must be equally acceptable to assume that the man is blind, as in dyj’s answer.

2. Further, if the wife was in the bedroom, how on earth could she know that the time left is EXACTLY 9 min 11 sec., not a second more and not a second less?

Yet another version of the ‘hang me – shoot me’ paradox puzzle. Just tell that the person would do what (s)he had promised to do if the statement is wrong. Then, if the statement is deemed true, the person will have to do the opposite, which, in turn, would make the sentence false, thus landing him / her in paradox.