Question

If your salary is increasing at a rate of 3.5% per year, about how long will it take your salary to double?

Answer 1

The answer is about 20.15 years ie 20 years 1 month and 24 days.
to solve it first you would have to pick just about any arbitrary  salary value eg:lets say $3000.so now you plug the value in this formula:
$p(1+ \frac{the_. percentage}{100} )^x$
 where p is the principle value or rather the initial value and x is the time during which the money changes.now we have  to find x since we the 3000 and 6000 (the double of 3000) and the percentage per year which is 3.5.plugging in the values into the formula we get:
$6000=3000(1+ \frac{3.5}{100} )^x$

now we solve for x using a scientific calculator and we get 20.14879168
we convert to 2 decimal place and get 20.15 year.
btw once you got the years now u can insert any value of your salary and assuming  that the 3.5% remain constant you should be able to obtain just about the double of your salary.
hope that helped :)