A sum of taka 725 is lent in the beginning of a year at a certain rate of interest. After 8 months, a sum of Tk. 362.50 more is lent but at the rate twice the former. At the end of the year, Tk. 33.50 is earned as interest from both the loans. What was the original rate of interest?

Created: 1 year ago | Updated: 1 year ago

Updated: 1 year ago

Let, real rate of interest r%

$∴$ New rate of interest (2r)%

According to the question

$\frac{725 \times r \times 1}{100} + \frac{362.50 \times 2 r \times 1}{100 \times 3} = 33.50 = \frac{2175 r \times 725 r}{300} = 33.52 = r (2175 + 725) = 10050 = r = \frac{10050}{2175 + 725} = \frac{10050}{2900} = 3.46 ∴ r = 3.46 R e a l r a t e o f i n t e r e s t i s 3.46 %$