Question

The way of selecting 4 letters from the word 'examination' is ​

Answer 1

Answer:

136 ways are there

Step-by-step explanation:

As pointed out, there are 3 different cases possible.

{abcd} - all 4 letters are distinct: C48=70C84=70;

{aabc} - two letters are alike and other two are distinct: C13∗C27=63C31∗C72=63 (C13C31 is a # of ways to choose which two letters will be alike from 3 pairs and C27C72 # of ways to choose other two distinct letters from 7 letters which are left);

{aabb} - two letters are alike and other two letters are also alike: C23=3C32=3 (C33C33 is a # of ways of choosing two pairs of alike letter from 3 such pairs);

Total=70+63+3=136.