At what rate percent compound interest per annum will Rs 640 amount to Rs 774.40 in 2 years? Let the rate of interest be R % .Then, \[A = P \left( 1 + \frac{R}{100} \right)^n \]\[774 . 40 = 640 \left( 1 + \frac{R}{100} \right)^2 \]\[ \left( 1 + \frac{R}{100} \right)^2 = \frac{774 . 40}{640}\]\[ \left( 1 + \frac{R}{100} \right)^2 = 1 . 21\]\[ \left( 1 + \frac{R}{100} \right)^2 = \left( 1 . 1 \right)^2 \]\[\left( 1 + \frac{R}{100} \right) = 1 . 1\]\[\frac{R}{100} = 0 . 1\]R = 10 Thus, the required rate of interest is 10 % per annum. Concept: Rate Compounded Annually Or Half Yearly (Semi Annually) Is there an error in this question or solution? |