Number of methods to post 4 letters in 4 envelopes such that only 1 letter goes to the correct e

M4maths Previous Puzzles

15 Jun 2009 letters and envelopes

Number of methods to post 4 letters in 4 envelopes such that only 1 letter goes to the
correct envelope is:-

OPtion

1) 3,
2) 4,
3) 5,
4) 6,
5) 7,
6) 8,
7) 9,
8) 10,
9) 11,
10) 12,

Solution

a b c d
A C D B
A D B C
Similarly with B, C, D

Correct Option: 6 Best Solution (1)