36.A man has 10 friends whom he wants to invite for dinner. The number of ways in which he can invite at least one of them is:
[1] 1024
[2] 10!
[3] 1023
[4]10!
Answer:
Suppose the man has to invite only one of his friends (out of 10) for dinner, then we know that he has to choose one amongst his 10 friends. This can be done in: 10C1 ways
The key word in the question is: at least, this means the friend can call 1 or 2 or 3 or…10 friends over for dinner. Mathematically, this can be shown as:
Therefore, the man can invite his 10 friends in (1024 – 1) or 1023 ways.
