Solution:

The stranger said that he thought the room was his. If so, he must have had the keys to the room and thus he must not have knocked.

Solution:

12 minutes

Explanation:
Yes, surely they can all make it out of the cave.

First, father and mother will go. Time taken = 2 minutes.
Father comes back. Time taken = 2 + 1 = 3 minutes.
Both children go. Time taken = 3 + 5 = 8 minutes.
Mother comes back. Time taken = 8 + 2 = 10 minutes.
Mother and Father go. Time taken = 10 + 2 = 12 minutes.

Thus in 12 minutes, all of them will be out of the cave through the tunnel.

Solution:

The farmer will be able to sell 0 oranges because the tree gives mango, not oranges.

Solution:

Since the knife was in her hand which implies that she was planning to kill her husband "Inspector Montalbano".

Solution:

927

Explanation
1) 5 4 7 : 7 is placed correctly
2) 5 3 0 : None of the numbers is in the code
3) 2 5 9 : 2 & 9 are correct number of code but placed at wrong position
4) 7 0 6: Number 7 is there but placed at wrong position
5) 6 4 9: Number 9 is there but placed at wrong position

Solution:

Frost forms on the inside of the window, not the outside. So shweta could not have wiped it off to discover Mr.Ankit's body.

Solution:

A typical way will be to start thinking about summing up the distance that the bee will travel but that will be quite a tedious task. How about we offer you a much easy solution?

The tunnel is 200 miles long and the trains are running at as peed of 100 mph which means that they will collide exactly at the center of the tunnel and seeking their speed, they will collide after an hour.

Now consider the bee which is flying at a speed of 1000 mph and will keep flying till the train collides. As calculated, it will keep flying for an hour which means the distance that it will cover is 1000 miles.

Solution:

The number is 37.

The missing guess can be either 24 or 50 and the missing difference is 8.

Solution:

Steps
1. Monica go from side A to B for approx 59 minutes
2. Lisa then move back to side A for 2 minutes to fool guard. Now guard will think she is coming to side A.
3. then she again move toward B :-)

Solution:

288/61 hours (4 hours, 43 minutes and 17 seconds approx)

Explanation:
In 1 hour, the ratio of swimming pool filled by pipes:
1st pipe: 1/48
2nd pipe: 1/72
3rd pipe: 1/96
4th pipe: 1/6

All togther
1/48 + 1/72 + 1/96 + 1/6
=> (6+4+3+48) / 288 = 61/288.
=> 288/61 hours,

which is 4 hours 43 minutes and about 17 seconds.