Posted by **Stephanie** on Sunday, May 8, 2011 at 10:36am.

In the year 2000 there were 350 mobile phones users living in the small town of Phoneville. Since 2000 the number of residents using mobile phones has increased by 25% each year, that is, each year the number of mobile phones increases by a factor of 1.25

Calculate, to three significant figures, the number of mobile phone users after 19 years. You may find it useful to first devise a formula for the number of mobile phone users after n years.