# Practice Questions on Permutation-CombinationAptitude Questions and Answers

## Moderate Permutation-Combination Question - 36

 Q36. In a certain laboratory, chemicals are identified by a colour-coding system. There are 20 different chemicals. Each one is coded with either a single colour or a unique two-colour pair. If the order of colours in the pairs does not matter. What is the minimum number of different colours needed to code all 20 chemicals with either a single colour or a unique pair of colours?
 A. $7$ B. $6$ C. $5$ D. $8$

## Moderate Permutation-Combination Question - 37

 Q37. Six boxes are numbered $1,2,3,4,5$ and $6$. Each box must contain either a white ball or a black ball. At least one box must contain a black ball and boxes containing black balls must be consecutively numbered. Find the total number of ways of placing the balls.
 A. $15$ B. $29$ C. $21$ D. $36$

## Moderate Permutation-Combination Question - 38

 Q38. In how many ways can 6 green toys and 6 red toys be arranged, such that 2 particular red toys are never together whereas 2 particular green toys are always together?
 A. 11! × 2! B. 9! × 90 C. 4 × 10! D. 18 × 10!

## Moderate Permutation-Combination Question - 39

 Q39. There are five comics numbered from 1 to 5. In how many ways can they be arranged, so that part-1 and part-3 are never together?
 A. 48 B. 72 C. 120 D. 210

## Moderate Permutation-Combination Question - 40

 Q40. The number of ways which a mixed double tennis game can be arranged amongst 9 married couples if no husband and wife play in the same is:
 A. 1514 B. 1512 C. 3024 D. 3028
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