Solution:

The Order of stupidity in decreasing order(most stupid to least) is 4,1,2 and 3.

Explanation:
Cutting his own trunk so Guy-4 is most stupid.
Next is Guy-1 as he is gagging on a tree that is to be cut down by guy-2.
Next is Guy-2 as he is not considering him to go down.
Guy-3 is a bad person but not a stupid one.

Solution:

It can be solve as shown below.

Solution:

Yes, you should switch the envelope. In the beginning when you picked up the envelope, you had a 1/3 probability of finding an offer letter in the envelope. There was 2/3 chance that the letter was there in the two envelopes on the table.

If you keep your selected envelope, you still have a 1/3 chance of finding an offer letter in that. However, since the interviewer has removed one empty envelope from the table, if you switch, you have a probability of 2/3 that the offer letter is inside that.

Solution:

If you see the picture, they formed a pentagonal shape and achieved the required.

Solution:

C7 => B8
Exchange pawn for a knight

Check-Mate

GameOver

Solution:

Take 10 number of cards in a new deck and change their face direction. For example- You create a new deck of 10 cards and out of 10, 3 faces up in the new deck. So remaining 7 faces up are in the old deck. But hey! while creating the new deck you reversed the face direction of new cards. So actually the 3 cards which were facing up are actually face down in the new deck while 7 faces up.

Solution:

I + IX = X

The equation read from the other side becomes X = XI + I which is false.

Solution:

The mules is moving in circular path and hence outside legs travels more distance than inner legs.

Solution:

2100 miles.

Each vowel equivalent to 500 and each consonant equivalent to -200

Solution:

It can be down as shown below.

Solution:

0%

Explanation:
1) why cant be 1/4 : If the answer is 1/4, then as we know two out of four answer choices is '1/4', the answer has be 1/2.
This is a contradiction, so the answer cannot be 1/4.

2) why cant be 1/2 : If the answer is 1/2 then because answer:"1/2" is 1 out of 4 answer choices, the answer must be 1/4. This is also a contradiction. So the answer cannot be 1/2.

3) why cant be 1 : If the answer is 1 then because answer:"1" is 1 out of 4 answer choices, the answer must be 1/4. Again the same contradiction and therefore answer cannot be 1.