| ... From Page 2 |
Counting Principle of Addition
If a total event can be accomplished in two or more mutually exclusive alternative-events (alternative ways), then the number of ways in which the total event can be accomplished is given by the sum of the number of ways in which each alternative-event can be accomplished.Number of ways in which the total event can be accomplished
= (Number of ways in which the first alternative-event can be accomplished)
+ (Number of ways in which the second alternative-event can be accomplished)
+ (Number of ways in which the third alternative-event can be accomplished)
+ ....
⇒ nE= nEa × nEb × nEc + ....
| Eg: | 1. |
Consider choosing a committee of 4 members from a group of 6 men and 5 women such that there are atleast 2 women in the committee.
In finding the number of ways in which the committee can be chosen, we identify that the total event can be accomplished in three alternative ways
[The events are mutually exclusive because, if the committee is chosen in one of these ways we can say that it was not chosen in the other ways (occurrance of one of these evnets prevents the occurance of the others)]
There are three alternative ways for accomplishment of this event ⇒ The number of ways in which the committee can be chosen to have
Therefore,
= [No. of ways in which the committee with 2 women and 2 men + [No. of ways in which the committee with 3 women and 1 man + [No. of ways in which the committee with 4 women and 0 men
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| Author Credit : The Edifier | ... Continued Page 4 |
