"Like if I have 5 tshirts and i want to gift them to my 5 cousins named A,B,C,D,E, so find number of ways in which particular cousin won't get their particular tshirts." So number of ways: D(n)=n!*(1-1/1!+1/2!-1/3!+.....(-1)^n*1/n!)) Where...
Que : Average of 5 consecutive even numbers is 12 . Find the sum of 1st and last numbers. Sol : shortcut... If consecutive numbers average is given, then average is (1st + last)/2 = 12 Therefore sum of 1st and last = 12*2 = 24