generating an equation for a problem

I am trying to help my grade 9 daughter solve this problem

Man has e mail about concert

Man sends email to 10 friends on day 1 so 10 people know about event

Each friend send e mail to 2 friends on day 2 so 20 people knows about event

Each of these 20 people sends email to 2 people on day 3 so 40 knows about event

Assume there are 5000 people in the town with e-mail and assuming mail only gets forwarded to people who have not already received it , how many days will it take before all 5000 people know about the concert.

Please kindly show the steps if possible.

Generating an Equation for a Problem

Thanks ADARSH my goal was to demonstrate to the kids that the computer is a great resource and is good for much more than Vibe or Youtube. Yout\r time is greatly appreciated.

Clemkonan