There are 6 letters for 3 envelopes. In how many different ways can the envelopes be filled? Choose the correct choice from the following answers
A) 120 B) 130 C) 100 D) 110 E) 140
The 1st envelope can be filled up in 6 ways.   The 2nd envelope can be filled up in 5 ways and the 3rd envelope can be filled up in 4 ways.   Therefore, by the principle of association, the three envelopes can be filled up in 6 x 5 x 4 = 120 ways   120NSWER:120
<result>A</result>
There are 6 letters for 3 envelopes. In how many different ways can the envelopes be filled?