remainder oh remainder
Level
2
1×1! + 2×2! + 3×3!......10×10! , what is the remainder when it is divided by 11
The answer is 10.
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1 solution
U can convert it into summation as r.r!, which u can rewrite as (r+1-1)r! Which is nothing but (r+1)!-(r)! And thus it becomes a telescopic , with end result as 11!-1 now as 11! Is divisible by 11, -1 can be written as 10-11 thus leaving remainder as 10