The sum 10∑k=1k.k! equals
10∑k=1k.k!
10∑k=1[(k+1)k!−k!]
10∑k=1((k+1)!−k!)
(2!−1!)+(3!−2!)+(4!−3!)+(10!−9!)+(11!−10!)
=11!−1
If (10)9+2(11)1(10)8+3(11)2(10)7+...+10(11)9=k(10)9, then k is equals to: (IIT JEE Main 2014)