Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa
  • Home
  • NCERT
  • Using the digits 1, 2, 3, 4, 5, 6, 7, a number of 4 different digits is formed. Find a)How many numbers are formed i)840

Using the digits 1, 2, 3, 4, 5, 6, 7, a number of 4 different digits is formed. Find 

\begin{array}{|l|l|l|l|} \hline \mathbf{C}_{\mathbf{1}} & & \mathbf{C}_{\mathbf{2}} & \\ \hline \text { (a) } & \begin{array}{l} \text { how many } \\ \text { numbers are } \\ \text { formed? } \end{array} & \text { (i) } & 840 \\ \hline \text { (b) } & \begin{array}{l} \text { how many } \\ \text { numbers are } \\ \text { exactly divisible } \\ \text { by 2? } \end{array} & \text { (ii) } & 200 \\ \hline \text { (c) } & \begin{array}{l} \text { how many } \\ \text { numbers are } \\ \text { exactly divisible } \\ \text { by 25? } \end{array} & \text { (iii) }&360 \\ \hline \text { (d) } & \begin{array}{l} \text { how many of } \\ \text { these are exactly } \\ \text { divisible by 4? } \end{array} & \text { (iiv) } & 40 \\ \hline \end{array}

 

Answers (1)

Given :Total number of digit to be formed=4 

 a. How many numbers are formed=^7P_4=840

 b. How many numbers are exactly divisible by 2? 

     Number ending with 2= ^6P_3=120

     Number ending with 4 = ^6P_3=120

     Numbers ending with 6 = ^6P_3=120

     So, total numbers=120+120+120=360

 c. Numbers exactly divisible by 25=40

 d. The numbers which have last 2 digit divisible by 4 are 12, 16 , 24 , 32, 36 , 44 ,52, 56, 64, 72, 76  So =  ^{11}P_2*^ 5P_2=200

Posted by

infoexpert21

View full answer

Similar Questions

Latest Question