Question 2 and 3, Review Exercise 6
Solutions of Question 2 and 3 of Review Exercise 6 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 2
How many words can be formed by using four distinct alphabets?
Solution.
Number of word we can make using $4$ different alphabets out of $26$ alphabets is
$$^{26}P_4=358800$$
Question 3
How many $3$-digit numbers are there which have $0$ at unit place?
Solution.
In $3$ digit numbers unit, tens and $100's$ place may be filled in 10 ways using digits #0# to $9$.
So total possible $3$ digit numbers are $$=10\times 10\times10=1000$$
If we fix units place at $0$ remaining two places may be filled in $10$ ways,
so total possible $3-$digit numbers having $0$ at units place are $$=10\times 10=100$$
Go to