Combinations
Combination
Each of the groups or selections that can be made by taking some or all of a number of things without considering the arrangement or order is called a combination.
Thus, the selections that can be made by taking the letters a, b and c two at a time are three. i.e., ab, bc and ac. These three groups or selections are called the combination of three things taken two at a time.
The number of combinations of n dissimilar things taken r at a time is calculated using the expression
For Example: The number of selection of 6 dissimilar things taken 4 at a time is
The number of combinations of n dissimilar things taken all at a time is
Also,
For Example: The number of selection of 3 dissimilar things taken all at is a time
Illustration: Each person's performance compared with all other persons is to be done to rank them subjectively. How many comparisons are needed in total, if there are 11 persons ?
(a) 66 (b) 55 (c) 54 (d) 45
Answer : b
Solution Comparison is always done between two peoples, we have to select 2 persons among the 11 persons for a comparison. Hence
How many committee of five persons with a chairperson can be selected form 12 persons? | |||
| Right Option : B | |||
| View Explanation | |||
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10thAbhyas institute is one of the best coaching institute in the vicinity of Ambala Cantt area. The teachers of the institute are well experienced and very helpful in solving the problems of the students.The good thing of the institute is that it is providing extra classes for the students who are w...
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