Exponential functions are in the form 
, where <em>a</em> is the initial value, <em>b</em> is the growth rate (percent increase) + 1, and <em>x</em> is the number of time periods. Our initial value is 100, and we're given the growth rate + 1 (tripling is the same as increasing by 200%; 200%=2.0; 2.0+1=3). Therefore our function is 
.