My math teacher gave us a task:
There are 30 students each student sends an e-mail with a message to 2 other people. And everybody who recieved this e-mail sends it again to 2 other people and so on.
The Question: How much rounds does it take to inform 25000 people.
For me its obvious that it takes 9 rounds. But my Math teacher doesn't share this opinion he says that it takes 10 rounds. And to proof his opinion he uses the formula: f(x)=30*2^x . but I think this formula is basically wrong and this is the right formula: f(x)=((30*2^x)*2)-30 .
Chart to prove my opinion:
So my question is who is right?