Classical

Permutations and Combinations Questions - Permutation and Combinations

36:  

There are three identical red balls and fouridentical blue balls in a bag. Three balls are down. The number of different colour combination is

A.

20

B.

35

C.

40

D.

30

 
 

Option: D

Explanation :


37:  

How many five different letter words can be formed out ofthe word "LOGARITHMS"?

A.

20120

B.

30120

C.

30240

D.

40840

 
 

Option: C

Explanation :

Total letters in the word "LOGARITHMS" is 10,i.e. n=10 and we have to form five-letter words
r = 5 Required number of words,

           = 10 x 9 x 8 x 7 x 6

           = 30240


38:  

Given npr = 3024

Value of r will be

A.

3

B.

4

C.

6

D.

9

 
 

Option: B

Explanation :

Since npr is product of consecutive positive integers.

npr = 3024 = 9 x 8 x 7 x 6

Hence,        r = 4


39:  
In a factory for five jobs the members A, B, C, D, E are eligible.
First three jobs can be filled in how many ways?
A.

20

B.

30

C.

60

D.

120

 
 

Option: C

Explanation :

First three jobs can be filled by 5 members in 5P3 ways.

Number of ways of filling the first 3 jobs

 5P= 5 x 4 x 3 = 60 ways


40:  

How many ways can 5 men and 3 women be seated in a row so that two women cannot sit side by side?

A.

120

B.

240

C.

1200

D.

14400

 
 

Option: D

Explanation :




Suggest an improvement