What is the value of 1 × 1! + 2 × 2! + 3 × 3! + . . . . . . . . n × n!
where n! means n factorial or n(n-1) (n-2) . . . . . . . . 1
A. n × (n - 1) × (n - 1)!
B. (n + 1)! - {n × (n - 1)}
C. (n + 1)! - n!
D. (n + 1)! - 1!
Answer: Option D
Solution(By Examveda Team)
1 × 1! = (2 - 1) × 81! = 2 × 1! - 1 × 1! = 2! - 1!2 × 2! = (3 - 1) × 2! = 3 × 2! - 2! = 3! - 2!
3 × 3! = (4 - 1) × 3! = 4 × 3! - 3! = 4! - 3!
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n × n! = (n + 1 - 1) × n! = (n + 1) (n!) - n! = (n + 1)! - n!
Summing up all these terms, we get (n + 1)! - 1!
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Comments ( 2 )
Related Questions on Permutation and Combination
A. 3! 4! 8! 4!
B. 3! 8!
C. 4! 4!
D. 8! 4! 4!
A. 7560,60,1680
B. 7890,120,650
C. 7650,200,4444
D. None of these
A. 8 × 9!
B. 8 × 8!
C. 7 × 9!
D. 9 × 8!
not getting
Above solution not understand pls help