The letters of the work ‘MANKIND’ are written in all possible orders and arranged in serial order as in an English dictionary. Then the serial number of the word ‘MANKIND’ is ______.
Arranging letters in alphabetical order A D I K M N N to find rank of MANKIND and making arrangements of a dictionary we get
A ………….\(\frac{6!}{2!}\)=360
D …………. 360
I …………. 360
K …………. 360
M A D ………….\(\frac{4!}{2!}\)=12
M A I ………….12
M A K ………… 12
M A N D …………. 3! = 6
M A N I …………. 6
M A N K D …………. 2
M A N K I D …………. 1
M A N K I N D …………. 1
∴ Rank of MANKIND = 1440 + 36 + 12 + 2 + 2
= 1492
If all the words with or without meaning made using all the letters of the word "KANPUR" are arranged as in a dictionary, then the word at 440th position in this arrangement is:

Nature of compounds TeO₂ and TeH₂ is___________ and ______________respectively.
Permutation is the method or the act of arranging members of a set into an order or a sequence.
Combination is the method of forming subsets by selecting data from a larger set in a way that the selection order does not matter.