# Can I use the approximate UDD formula for annuities payable pthly?

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In a test or exam, when calculating the annuity payable p-thly, can I apply the approximate UDD assumption? i.e. set alpha(m)=1 and beta(m)=(m-1)/(2m)

It's fairly accurate and a lot faster than using the direct UDD or Woolhouse formula. This comes up a lot in pensions.

Thanks!