Your goal is to create a college fund for your child. suppose you find a fund that offers an apr of %4%. how much should you deposit monthly to accumulate ���$81,000 in 12 ���years?

This is known as a monthly annuity.
You will need a special formula (See attached).
rate = 4/1,200 = 0.0033333333
number of months = 12*12 = 144
Monthly Amount = Total / ([(1+r) ^ (n+1) -1] / [r]) -1
Monthly Amount = 81,000 / [(1.0033333)^(145) -1] /  .0033333333] -1
Monthly Amount = 81,000 / [1.6201675397 -1] / [.0033333333] -1
Monthly Amount = 81,000 / [.6201675397 / .0033333333] -1
Monthly Amount = 81,000 / [186.0502637705 -1]
Monthly Amount = 81,000 / 185.0502637705
Monthly Amount = 437.71
Here's a monthly annuity calculator to check your work:
http://www.1728.org/annuitym.htm