Q30 of 31 Page 7

From a class of 25 students, 10 are to be chosen for an excursion party. There are 3 students who decide that either all of them will join or none of them will join. In how many ways can the excursion party be chosen?

Case 1: When all 3 joins.


Remaining 7 people are to be chosen from 25-3 = 22 people.


Number of ways = 22C7




= 170544


Case 2:


When all 3 don’t join.


Remaining 10 people are to be chosen from 25-3 = 22 people.


Number of ways = 22C10




= 646646


Total ways = 170544 + 646646


= 817190


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