Saving for retirement by contributing the same amount each month from your 23rd birthday until your 65th birthday, in an account that pays a steady 4% annual interest compounded monthly.

How much will be in your fund at age 65 if you save $100 a month?

monthly rate = .04/12 = .003333...

time from 23rd to 65th birthday = 504 months

amount = 100( 1.003333..^504 - 1)/.003333..
= $130,517.61

To calculate the amount in the retirement fund at age 65, we can use the formula for the future value of an ordinary annuity:

Future Value = P * ((1 + r)^nt - 1) / r

Where:
P = Monthly contribution amount ($100)
r = Annual interest rate (4% / 12)
n = Number of compounding periods per year (12)
t = Number of years (65 - 23 = 42)

Let's substitute the values into the formula and calculate:

P = $100
r = 4% / 12 = 0.04 / 12 = 0.00333 (rounded)
n = 12
t = 42

Future Value = $100 * ((1 + 0.00333)^(12*42) - 1) / 0.00333

Calculating this, the future value of the retirement fund at age 65 will be approximately $176,694.73.