We would apply the formula for calculating the future value of an ordinary annuity. It is expressed as
S = R[((1 + i)^n - 1)/i
where
R is the payment at the end of each period
i is the interest rate per period
n is the number of periods
S is the future value
Since the deposit is monthly, i = r/12
where r is the interest rate
From the information given,
r = 5% = 5/100 = 0.05
i = 0.05/12 = 0.00417
R = 100
number of years = 65 - 24 =41
number of periods, n = 41 x 12 =492
By substituting these values into the formula, we have
S = 100[((1 + 0.00417)^492 - 1)/0.00417
S = 100[((1.00417)^492 - 1)/0.00417
S = 161637.31
The IRA will contain $161637.31 when he retires at 65
Total deposit made over the time period = 100 * 492 = $49200