Calculating Probability of Receiving $1 from Multiple People

[damajha]

Should be simple enough... unfortunately I'm 20 years removed from college and can't seem to find an equation so I thought I'd post it here.

If there is a 30% chance that Bob will give me a $1, and a 30% chance that Ted will give me a $1 and a 30% chance that Frank will give me a $1. What are the chances that at least one of them gives me a $1?

Very hypothetical, but if someone could give me the equation to solve it then I can figure some other problems out on my own.

Thanks,
Dale

 

[CRGreathouse]

The chance that at least one will give you a dollar is 100% minus the chance that none will give you a dollar. The chance that none will give you a dollar is the chance that the first won't give you a dollar times the chance the second won't times the chance the third won't.

 

[damajha]

So... if I get this straight

1 - (.7 x .7 x .7) = 65.7% ?

 

[vela]

Yup, or you can look at all the combinations that can occur, e.g. Bob gives you a dollar and Ted and Frank don't, and so on, and then sum the appropriate probabilities.