Statistics - Permutations 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?
- 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
- Option : D
- Explanation : 5 jobs can be filled by 5 members in 5P5 ways.
5P5 = 5 ! = 5 x 4 x 3 x 2 x 1
= 120 ways.
- 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 of R
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