What is the interest earned on this investment ? 31,000 per year for 30 years becomes 23,10,000 .

Annuity formula is :

Maturity value = Amount paid per year * [ {(1+r)^n – 1}/r ] * (1+r)
Here n = 30 years
and r = rate of interest earned
Putting all these values

23,10,000 = 31,000 * [{(1+r)^30 -1}/r] * (1+r)

The value of r which satisfies this equation is 5.4 .

ref:http://www.jagoinvestor.com/2008/10/why-endowment-policy-are-never-best_08.html
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