Solution:

Explanation:

Since Rohini is 21st from either side, there must be 20 people in front of her and 20 people behind her.
20 + 20 + 1 (she herself) = 41
Therefore, the queue consists of 41 people.

Solution:

See the colored sticks in the picture. We have moved those sticks in the position given in the second image corresponding with the color.

Solution:

Rhea will open just one present.
Cindy|Y - Y is the 25th alphabet
Duk|E - E is the 5th alphabet
Joh|N - N is the fifteenth alphabet
Rhe|A - A is the first alphabet

Solution:

2 minutes (duration between 9:59 and 10:01)

Solution:

7, 4, 6, 5, 8

Solution:

   9567
+ 1085
======
 10652

Solution:

Sam : 2
Dean : 5
Castiel : 7

Age diff
7 - 2 = '5' is prime
7 - 5 = '2' is prime
5 - 2 = '3' is prime

Solution:

The three errors are as follows:
a) fynd is spelled wrong. The correct spelling is 'find'.
b) that is not appropriate to use here. It should be 'this'.
c) There are only two errors in the question and that is the third error because the questions asks us to find three.

Solution:

7

Explanation:
8th is bald man head, check the video below.

Solution:

He should draw any chit of paper and before unfolding it, he must eat and swallow the chit. In this manner, to determine the judgment of the god, they will have to look at the other chit which will have 'Guilty' written over it. Thus everyone will believe that the chit which he ate had innocent written over it and thus they will believe that he is innocent.

Solution:

Put one red marble in one box and all other marbles in the 2nd box.

Probability :
50 + 24/49