If the number of users tripled every year since 2001, and there were 3 million users in 2005, how many were there in 2004?

Question

im stuck on this i need help 

Answer 1

Say there are x users in 2004, since the uses tripled every year, then there will be 3x users in 2005:

 

3x=3 million  -> x= 1 million

Answer 2

If the number of users triple every year then   Y_n+1 = 3Y_n

 

This means that for any given year...  Y_n+1 = (1/3)Y_n

 

In other words, the year before will be one third of the current year

 

3,000,000/3 = 1,000,000 users in 2004