Question

Rs 3600 was invested in banks X and Y at the rates of 10% simple interest amd 15% compound interest respectively . find the interest received in 2nd year if the interest received in the 1st year from the two banks differed by Rs390 ..​

Answer 1

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Given :

Simple interest for two years = 600

Compound Interest for two years = 615

Analysis/Interpretation :

SI for first year = 300

SI for second year = 300

CI for first year = 300

CI for second year = 315

The additional CI of Rs 15 is interest on Rs 300 interest received in first year. So rate of interest is 15/300 x 100 = 5%.

Now, interest of Rs 300 at the end of first year @ 5% pa means principal at the beginning of the year is :

P = 300/5 x 100 = Rs 6000

Note that no formulae for SI or CI is used in the answer and the solution is based on understanding of core concept.