Slater begins saving for college tuition. he invests $1000 in an account that pays 2.5% simple interest. how many years before his account has reached $1500?

The formula is Interest = principle times rate times time in years.
                        I=prt        

p=1000
r= 0.025
t=x

To find the amount of interest that is earned in a specific time frame, subtract the final amount of money by the principal. 1500-1000=500.

500 = 1000(0.025)x
500 = 25x   
x= 20 years