Question
Mathematics Question on permutations and combinations
1.1! + 2.2! + 3.3! +.....+ 10.10! =
A
11!
B
11! + 1
C
11! - 1
D
11.10!
Answer
11! - 1
Explanation
Solution
1.1! + 2.2! +.....+ n.n! = (n + 1)! - 1 ⇒ 11! - 1
1.1! + 2.2! + 3.3! +.....+ 10.10! =
11!
11! + 1
11! - 1
11.10!
11! - 1
1.1! + 2.2! +.....+ n.n! = (n + 1)! - 1 ⇒ 11! - 1