Ask Questions, Get Answers

Want to ask us a question? Click here
Browse Questions
Home  >>  CBSE XI  >>  Math  >>  Permutations and Combinations
0 votes

Using the digits 1,2,3,4,5,6,7,a number of 4 different digit is formed.Find (c) How many numbers are exactly divisible by 25

$\begin{array}{1 1}(A)\;40\\(B)\;25\\(C)\;50\\(D)\;75\end{array} $

Can you answer this question?

1 Answer

0 votes
The no.divisible by 25 should end with 5
Thus the last two digit should be 25 or 75 for other 2 digit no. we have =$5P_2$
$\Rightarrow \large\frac{5!}{3!}$
$\Rightarrow \large\frac{5\times 4\times 3!}{3!}$
$\Rightarrow 20$
Hence if the last two digit is 75
The no. of ways will be 20
Thus the total no. of way =20+20
$\Rightarrow 40$
Hence (A) is the correct answer.
answered May 19, 2014 by sreemathi.v

Related questions

Ask Question
student study plans
JEE MAIN, CBSE, AIPMT Mobile and Tablet App
The ultimate mobile app to help you crack your examinations
Get the Android App