what is probabability that 5 envelope can not put in to the right envelope?
Answers
A) 11/30  B) 12/30  C) 13/30  D) 14/30  E) 15/30
Number of derangements = n! (1/2! - 1/3! + 1/4! + ... + ((-1)^n)/n!)   Given 5 letters A, B, C, D and E:   Total number of derangements = 5! (1/2! - 1/3! + 1/4! - 1/5!) = 60-20+5-1= 
<gadget id="calculator">60-20+5-1</gadget>
<output>44</output>
44.   Total possible arrangements= 5! = 120.   P(no letter is in the correct position) = 44/120 = 11/30.   11/30NSWER:11/30
<result>A</result>
what is probabability that 5 envelope can not put in to the right envelope?