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Re: permut&combi
by sahil sharma - Thursday, 26 February 2015, 08:47 AM
  Total answer is 7!*104
Case 1: Where we place one letter in row one, one in row two and 5 in row 3. total ways = 2*2*6C5
Case 2: One letter in row and 2 in row 2 and 4 in row 3
total ways = 1*2*6C4
Case 3 : 2 letters in row and 1 in row 2 and 4 in row 3
total ways = 1*2*6C4
Case 4 2 letters in row 1 and 2 and 5 in row 3
total ways = 1*1*6C3

IN all these cases we will have 7! ways to arrange the letters

Hence total ways = (case1+case2+case3+case4)*7!

= 104*7!
= 13*8!