For what value of n is
1 ( 1 ! ) + 2 ( 2 ! ) + 3 ( 3 ! ) + . . . + 2 0 1 4 ( 2 0 1 4 ) ! = n ! − 1
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Nice solution...
great answer
Great solution.
pretty solution.
gddd answer
Here is another way. 1(1!)+2(2!)+..+2014(2014!)={2(1!)+3(2!)+...+2015(2014!)} -{1!+2!+...+2014!}={2!+3!+...+2015!}-{1!+2!+...+2014!}=2015!-1
Great solution! Very simple.
Just hit n trial!.consider first two terms which is 1+4=5=3!-1.Now consider first three 1+4+18=23=4!-1. The last no of the series is 2014,therefore the ans is 2015
That's one way. But, there is a more of a logical way to solve this :D
by mathematical induction we can prove that 1.1! + 2.2!+..............+ n.n! = (n+1)!-1 hence here n = 2014 so n +1 = 2015
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1 . 1 ! + 2 . 2 ! + 3 . 3 ! + . . . . . + n . n ! = ( 2 − 1 ) 1 ! + ( 3 − 1 ) 2 ! + ( 4 − 1 ) 3 ! + . . . + [ ( n + 1 ) − 1 ] n ! = 2 ! − 1 ! + 3 ! − 2 ! + 4 ! − 3 ! + . . . . . . + ( n + 1 ) ! − n ! = ( n + 1 ) ! − 1 !
H e r e , t h e v a l u e o f n i s 2 0 1 4 . S o , t h e a n s w e r i s 2 0 1 5 .