Can you consider this an arithmetic or geometric sequence?

Hey I have a couple of question that I need answered the soonest this week. See below:

Suppose you are provided with a geometric sequence. How can you find the sum of n terms of the sequence without having to add all of the terms?

Suppose a rumor is spread by first one person telling another individual and then the individual telling two other people. Each person in turn tells two other people. Can you consider this an arithmetic or geometric sequence? Explain your answer.