What is the value of a principle after 30 DAYS for an annual interest compounded annually?

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If an amount of $1,000 \$$ is deposited into a savings account at an annual interest rate of 10%, compounded yearly, what the value of the investment after 30 DAYS?
Can anyone help me with this?
Is it enough to just do $A = (1 + r/n)^{nt}$ and convert $t$ to days instead of years?
I did that, $1000\times(1+0.1/1)^{30/365}$, and I get $1007.36$. But plugging the same values in this calculator gets me the result $1008.22$. Which is correct? What am i doing wrong?

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The correct answer is given by the calculator. In your case the compounding period is bigger than the saving period. Then it is common to use the simple interest.

$$C_{30}=1000\cdot \left(1+0.1\cdot \frac{30}{365}\right)=1,008.22$$


Similiar case if the saving period is not a multiple of the compounding period. Let´s say the saving period is $400$ days and the compound period is still $365$ days.

The first $365$ days it is compunded with $10\%$. Then for the remaining $35$ you use the simple interest.

$$C_{400}=1000\cdot 1.1\cdot \left(1+0.1\cdot \frac{35}{365}\right)=1,110.55$$