Math
posted by Naimy .
Suppose you deposit $400 in an account that earns 0.75 percent each quarter. You make no withdrawals from the account and deposit no more money into the account. How much money will accumulate after 2.5 years?

how about
400(1.075)^10 ?
or $824.41 
At 0.75 percent, I don't think you'd more than double your money in just 2.5 years.
I got a different answer. I used 0.0075 as the multiplier and figured it the long way  quarter by quarter.
In the first quarter you'd earn $3.00. Add that to the original 400 and again multiply by 0.0075. At the end of the second quarter, you'd have $406.02.
Finally, by the end of the 10th quarter, I got a total of $431.03. 
of course!
I left out a zero, and then punched in that wrong value in my calculator, without thinking about the answer.
should have been
400(1.0075)^10
= 431.03
thanks for catching that 
You're welcome, Reiny.