Question

please solve this problem for me

Answer 1

nitthesh is sending it is right answer

Answer 2

Ans 
 i)7 books can be arranged on a shelf in 5040 ways
ii)3 books are always together by arranging them in 6 ways    

Explanation:
i) It is because these no/s based on  permutations 
The Maths behind it is
          1#)one book     = 1 way                           (1×1)
          2#)two books    = 2 ways (2×1#)              (2×1) 
          3#)three books = 6 ways (3×2#)               (3×2)
          4#)four books   = 24 ways (4×3#)             (4×6) 
          5#)five books    = 120 ways (5×4#)           (5×24)
          6#)six books     = 720 ways (6×5#)           (6×120)  
          7#)seven books= 5040 ways(7×6#)          (7×720) 
ii)Arranging of three books in same order
           720 ways as three books of the books can be arranged in two order when kept one as constant 
For ex   A B C
            A C B
Then,(3×2)# = 6#   =  720 ways 

:) Hope this Helps!!!