Statistics - Permutations and combinations

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

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37. How many five different letter words can be formed out of the word "LOGARITHMS"?

  • 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,

    Permutation and Combination

     = 10 x 9 x 8 x 7 x 6

     = 30240

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38. Given nPr = 3024

Value of r will be

  • Option : B
  • Explanation : Since npr is product of consecutive positive integers.

    npr = 3024 = 9 x 8 x 7 x 6

    Hence,        r = 4

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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?

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

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