This is really simple.
Let's say the compounding frequency is x, mathematically, we have
(1+ 7.06%/x)^x =1+ 7.25%. Solve for x, which should be one of 4, 12, 52, or 365, corresponding to quarterly, monthly, weekly or daily compounding frequency, respectively. This equation cannot be solved for a closed form solution since it is not a normal function. However, we can still solve it either numerically or by trial and error.
To simplify the calculation, we could take the natural log on both sides and change the equation to its equivalent,
x*ln(1+7.06%/x) = ln(1+7.25%).
Using MS Excel, we have the following results,
| compounding frequency | | natural log of gross annualized interest rate (lefthand side) | | natural log of gross interest rate(righthand side) |
| Quarterly (x=4) |
| 0.06998419 |
| 0.069992372
|
| Monthly (x=12) |
| 0.070393129
|
| 0.069992372
|
| weekly (x=52) |
| 0.070552117
|
| 0.069992372
|
| Daily (x=365) |
| 0.070593173
|
| 0.069992372
|
| |
|
|
|
|
| Number of quarters |
| 7/3
|
| 2.333333333
|
| Initial deposit |
| 10000
|
|
|
| |
| 10000*(1+7.06%/4)^2.33333
| = | 10416.68871 |
We can see the quarterly compounding frequency leads to the annualized interest rate closest to the given one.
So we should use quarterly compounding.
The intesest the investor will receive 7 months later is 416.69 Yuan, rounding to Fen. Taking the principal into account,the bank will give 10416.69 Yuan in total back to the investor.
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NOTE: On the third line, one (1) was missing on the righthand side of the equality. I already added it to make the answer accurate. The remaining part is typo-free.