andy44 wrote:Back when Nathan was born, his mother deposited $1,000 in an account paying 6% compounded semi-annually. He has just turned 18.

A) How much money is in the account?

Use the compound-interest formula you've memorized:

. . . . ....where "A" is the ending amount, "P" is the beginning amount, "r" is the interest rate (as a decimal), "n" is the number of compoundings per cycle, and "t" is the number of cycles (usually "years"). In your case, the set-up would be:

. . . . .Of course, n = 2 because "semi-annually" means "twice a year".

Simplify to get your answer.

andy44 wrote:B) Suppose, on Nathan's 10th birthday, that his mother had been able to add $1,000 more to the account.what is the account balance at the end of the same 18 years?

This works just like the previous one, expect that it's in two pieces. You'd find the value at the end of the first ten years:

. . . . .Then you'd add another thousand bucks, and use this as your "P" in the second bit, being the last eight years:

. . . . .Try to "carry" as much as you can inside your calculator, so as to minimize round-off error.