Question

Find the no. of 4 letter words having equal no. of consonants & vowels.(repetition not allowed)

Answer 1

Answer:

Let us first select two places for vowel, which can be selected from 4 places in

4

C

2

ways. Now this places can be filled by vowels in

5×5=25 ways as repetition is allowed. The remaining two places can be filled by consonants in 21×21 ways. Then the total number of words is

4

C

2

×25×21

2

=150×21

2

.