Question 10 and 11, Exercise 6.2
Solutions of Question 10 and 11 of Exercise 6.2 of Unit 06: Permutation and Combination. This is unit of Model Textbook of Mathematics for Class XI published by National Book Foundation (NBF) as Federal Textbook Board, Islamabad, Pakistan.
Question 10
How many words can be formed from the letters of word “FRIDAY”? How many of them will end with “F”.
Solution.
Total letters of FRIDAY $=6$
No letter is repeated so possible permutations $={ }^{6}{ }^{1} P_{5}=6$ !
hence $720$ words can be formed.
For words ending at $F$ we fix $F$ at end and find possible arrangements for remaining $5$ letters which is $5!=120$
Question 11
How many differnt permutations of the word STATESMAN can be formed using all letters at a time?
Solution.
Total letters$=9$
Repetition of $S=2$
Repetition of $T=2$
Repetition of $A=2$
\begin{align*}\text{possible permutation}&=\dfrac{9!}{2!2!2!}\\
&=\dfrac{362880}{8}\\
&=45360\end{align*}
Go to