SOLUTION: In how many ways can one invite one or more of her seven friends to a party?

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Question 1119387: In how many ways can one invite one or more of her seven friends to a party?
Answer by Edwin McCravy(20064) About Me  (Show Source):
You can put this solution on YOUR website!

There are 2 decisions that can be made concerning friend #1, invite 
friend #1 or don't invite friend #1. That's 2 ways.

There are 2 decisions that can be made concerning friend #2, invite 
friend #2 or don't invite friend #2. That's 2 ways.

There are 2 decisions that can be made concerning friend #3, invite 
friend #3 or don't invite friend #3. That's 2 ways.

There are 2 decisions that can be made concerning friend #4, invite 
friend #4 or don't invite friend #4. That's 2 ways.

There are 2 decisions that can be made concerning friend #5, invite 
friend #5 or don't invite friend #5. That's 2 ways.

There are 2 decisions that can be made concerning friend #6, invite 
friend #6 or don't invite friend #6. That's 2 ways.

There are 2 decisions that can be made concerning friend #7, invite 
friend #7 or don't invite friend #7. That's 2 ways.

Answer = 2∙2∙2∙2∙2∙2∙2 = 27 = 128 ways.

Edwin