IMy stock porfolio of $500,000.00 will grow at 10% for the next 10
years. I am considering selling this porfolio ten years from now and
buying an annuity program that will pay me an equal amount at the end
of each year for the following ten years(i.e,year 11 to year 20 from
now.) If the annuity plan promises the same annual interest
rate(10%),how much will I receive each year from that annuity

Holla –

The type of annuity you describe is "single premium immediate annuity:
Travelers Life & Annuity
"Annuity FAQ" (2002)
Annuities are typically structured to defer taxable income.  

Annuities are typically structured to defer taxable income.  There are
no tax assumptions in this question, so none have been made in the
answer.  However, depending on whether the stock portfolio gains are
taxed at normal or lower "capital gains" rates and when the taxes fall
(annually or at year 10?), there can be dramatic changes in the
calculations.

The growth of the stock portfolio is easy: a 10% annual gain yields
$1,296,871 at the end of 10 years, growing to $1,426,558 in year 11
before the first annuity payment is made.

In the annuity, you'll be receiving principal AND interest back for
each of 10 years, drawing the balance to zero at the end of year 20. 
Unfortunately, most Internet annuity calculators want to assume a
lifetime annuity or monthly payments – which aren't part of this
question.

However, Microsoft Excel has a function called PMT (payment) that will
calculate the annuity knowing:
rate = .10 (for 10%)
# of payments = 10
present value = $1,296,871
future value = 0 after the last payment
type = payments due at the END of the period

The annual annuity payment is $211,060.

Google search strategy:
annuity + calculation

If any part of this is unclear, please let me know in a clarification
request before rating this question.

Best regards,

Omnivorous-GA