Q.Find the amount on ₹10,000 for 4 months at 12% per annum, compounded monthly.

For monthly compounding, divide the annual rate by 12 and use the number of months directly as the number of periods.

Rate per month $= 12/12 = 1\%$. …

Here $P = ₹10{,}000$, annual rate $r = 12\%$, time $= 4$ months, compounded monthly.

Step 1 — Find the number of monthly periods and the rate per month. Since the compounding is monthly, the number of periods is simply the number of months given, $= 4$. Rate per month $= \dfrac{r}{12} = \dfrac{12}{12} = 1\%$.

Step 2 — Apply the monthly formula.

$A = P\left(1+\frac{r}{1200}\right)^{12t} = 10{,}000\left(1+\frac{12}{1200}\right)^{4} = 10{,}000(1.01)^{4}$ …

Students often multiply the number of months by 12 again when the time is already given in months rather than years — here the number of periods is just 4 (the given months), not $12 \times 4$. Always check whether th …