Ans 2: (Master Answer)
Class : Class 1
The correct answer is C.
Handshakes by the first child = 6 (with remaining 6 children)
Handshakes by the second child = 5 (as the handshake with the first child is already counted)
Then, handshakes by the third child = 4 (as the handshakes with the first and second child are already counted)
Similarly, handshakes by the fourth, fifth and sixth child are 3, 2 and 1 respectively.
Since, the last child's handshakes are already counted, he/she will not make any new handshakes.
Therefore, a total of (6 +5 +4 + 3 + 2 + 1) = 21 handshakes took place.
Ans 3:
Class : Class 8
You have not told that once a person has done handshake with the other people , his /her handshake will not be taken again.
and 
= 1 whole, then 
= ?
