Question:

Out of 7 consonants and 4 vowels, how many words of 3
consonants and 2 vowels can be formed?

A. 25200 B. 21300

C. 24400 D.
210

## Answer:

3 consonants can be selected from 7 consonants in $^7C_3$ ways.

2 vowels can be selected from 4 vowels in $^4C_2$ ways.

$\therefore$ by multiplication principle,

the number of selecting 3 consonants and 2 vowels is

$=^7C_3 \times ^4C_2$

$=\frac{7!}{3!4!} \times \frac{4!}{2!2!}$

$=\frac{7.6.5}{3.2.1} \times \frac{4.3}{2.1}$

$=35 \times 6$

$=210$

Now, the number of ways of arranging 5 letters among themselves

$=5!$

$=120$

$\therefore$ the total number of words of 3 consonants and 2 vowels

$=210 \times 120$

$=25200$

## Post a Comment

If you have any question, please let me know by comment or email. Also, if you want answers of any mathematical problem, please comment me the question. I will post the answer as early as possible.