If a certain sum of money becomes double at simple interest

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If a certain sum of money becomes double at simple interest in 12 yr. What would be the rate of interest per annum ?

Let the amount be P, then amount after 12 yr = 2 P
SI = 2P - P = P
SI = (P x R x T)/ 100
P = (P x R x 12)/ 100
⇒ R = 100/12 = 8¹/₃%