Question

Find the rate of interest when Rs 640 amounts to Rs 841 and 60 paise for the period 2 years 7 months and 15 days at a simple rate of interest

Answer 1

Principal = Rs. 640 Amount = Rs. 841.60
Interest = $Rs.(841.60-640)=Rs.201.60$
Time = 2 years 7 months 15 days = $\frac{21}{8}$ years To find Rate (R)
Simple interest (I) = $201.60=640\times \frac{R}{100}\times \frac{21}{8}$
$\Rightarrow 640\times \frac{21}{8}\times \frac{R}{100}=\frac{20160}{100}$
$\Rightarrow R=\frac{20160}{100}\times \frac{1}{640}\times \frac{8}{21}\times \frac{100}{1}$
$\Rightarrow R=12$Hence rate of interest = 12%