Classical

Permutations and Combinations Questions - Permutation and Combinations

21:  

In a factory for five jobs the members A, B, C, D, E are eligible.

In how many ways the first two jobs can be filled?

A.

20

B.

30

C.

60

D.

120

 
 

Option: A

Explanation :

First job can be filled in 5 ways by anyone of the five numbers. Out of the five, if one is selected for the first job, then second job can be filled by the remaining 4 members in 4 ways. Hence number of ways of filling the first and second jobs = 5 x 4 = 20


22:  
In a factory for five jobs the members A, B, C, D, E are eligible.

All jobs can be filled in hcw many ways?

A.

20

B.

40

C.

60

D.

120

 
 

Option: D

Explanation :

5 jobs can be filled by 5 members in  5Pways.
 5P5 = 5 ! = 5 x 4 x 3 x 2 x 1 
= 120 ways.


23:  

If 6 identical coins are arranged in a row, then number of arrangements in which 4 are heads and 2 are tails are

A.

4

B.

6

C.

12

D.

15

 
 

Option: D

Explanation :


24:  

l'here are four bus lines between A and B; and three bus lines between Band C.

The number of ways a person can travel by bus from A to C by way of B will be

A.

10

B.

12

C.

14

D.

24

 
 

Option: B

Explanation :

There are four ways to go from A to B and three ways to go from B to C, Hence there are 4 / 3 = 12 ways to go from A to C by way ofR


25:  

The number of ways in which a team of eleven players can be selected from 22 players including 2 of them and excluding 4 of them is

A.

16C11

B.

16C5

C.

16C9

D.

20C9

 
 

Option: C

Explanation :




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