Compound Interest (Without Using Formula)

A = P + I

I = (P × R × T)/100

C.I. = A - P

C.I.(next period) = C.I.(current period) + Interest for one period on C.I.(current period)

Amount(next period) = Amount(current period) + Interest on Amount(current period) for one period

Year 1: Interest = (P × R × 1)/100, Amount = P + Interest

Year 2 onward: Interest = (previous amount × R × 1)/100

For half-yearly compounding: T = 1/2 year for each conversion period

For 2 1/2 years compounded annually: last 1/2 year uses simple interest on the last full-year amount

When rates differ each year: Interest for each year = (that year's principal × that year's rate × 1)/100