Combination!
Probability
Level
2
MR. X has 10 friends. Among them two are married to each other. She wishes to invite five of them for a party. Now, there is a problem----- the married couple refuse to attend separately.
Find no. of different ways MR. X can invite five friends.
56
None of these
140
126
112
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1 solution
Mr. X can invite his friends in two ways. With the couples or without them.
If he invites the couple then he can invite others in 8C3 = 56 ways.
If he doesn't invite them, then he can invite others in 8C5 = 56 ways.
So, he can invite his friends in 112 ways in total.