RRB NTPC - Permutations Combinations

1.

How many arrangements of the letters of the word BEGIN can be made, without changing the place of the vowels in the word? 

   A.) 7 ways
   B.) 6 ways
   C.) 5 ways
   D.) 2 ways

Answer: Option ''

Answer: Option 'B' 
E,I fixed. Consonants can be arrangements in 3P3 = 3! = 6 ways

2.

In how many different number of ways a combination of 3 men and 2 women can be selected from 6 men and 5 women.

   A.) 15
   B.) 20
   C.) 25
   D.) None of these

Answer: Option 'B'

6C3
= 6!/(3! . 3!)
= (6 × 5 × 4)/(3 × 2)
= 5 × 4 = 20.

3.

In how many different number of ways 4 boys and 2 girls can sit on a bench?

   A.) 620
   B.) 640
   C.) 720
   D.) None of these

Answer: Option ''

Answer: Option 'C'
npn = n! 
6p6
= 6 × 5 × 4 × 3 × 2 × 1 = 720

4.

Find 9P3

   A.) 414
   B.) 514
   C.) 504
   D.) None of these

Answer: Option 'B'

9P3 = 9!/6! = 9 × 8 × 7
= 504.

5.

In how many different number of ways 5 men and 2 women can sit on a shopa which can accommodate persons? 

   A.) 230
   B.) 203
   C.) 220
   D.) 210

Answer: Option 'D'

Answer: Option 'D' 
7p3 = 7 × 6 × 5 = 210

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