The names of 18 students of class 12 and 20 students of class 11 are selected to form a quiz team of 15 students. But 9 among them cannot join as they already left for the excursion. In how many ways can the team be made now?
Note the following:
The formula for the combination for the selection of the items from the
different items is
The restricted combination for the selection of the items from the
different items with
particular things always excluded is
Since 9 students must never be included in the team, the following is evident.
The number from which the restricted combination is to be made is .
The number with which the restricted combination is to be made is
Therefore, the required restricted combination is
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