OBTAINED at a sum for 4 years at r % = SI on the same sum at r % for 14 yearsFormula USED ;Amount = Principal + SI\(SI = {P\times r\times t \over 100}\)Calculation :Let the principal be PAccording to the QUESTIONTHE amount for 4 years at r % = SI for 14 years at r %P + SI for 4 years at r % = SI for 14 years at r %⇒ P + \({P\times r\times t \over 100}\) = \({P\times r\times T \over 100}\)P + \({P\times r\times 4 \over 100}\) = \({P\times r\times 14 \over 100}\)⇒ P = (14Pr/100) - (4Pr/100)⇒ P = Pr/10⇒ r = 10∴ The VALUE of 'r' is 10 %