Question

Find the principal, if the compound interest of two years of the rate
of compound interest 5% per annum is rupees 615.​

Answer 1

Answer:

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.

Cheers !!!!!

Answer 2

Answer:

let the principal be ₹p, amount will be=p+615

now,A=P(1+R/100)^n

P+615=P(1+5/100)²

P+615/P=441/400

P/P+615/P=441/400

1+615/P=441/400

615/P=441/400-1

615/P=441-400/400

615/P=41/400

41P=615×400

p=615×400/41

P=15×400

P=6000

so ,the principal is₹6000