Calculate the ratio of length of an open organ pipe to closed organ pipe if the fourth overtone of open pipe is in unison with the sixth overtone of closed pipe.

Explanation

To solve the problem of finding the ratio of the length of an open organ pipe to that of a closed organ pipe when the fourth overtone of the open pipe is in unison with the sixth overtone of the closed pipe, we can follow these steps:

### Step 1: Understand the Harmonics
- For an open organ pipe, the nth overtone corresponds to the (n+1)th harmonic. Therefore, the 4th overtone of the open pipe is the 5th harmonic.
- For a closed organ pipe, the nth overtone corresponds to the (2n + 1)th harmonic. Thus, the 6th overtone of the closed pipe is the 13th harmonic.

### Step 2: Write the Frequency Formulas
- The frequency of the nth harmonic for an open pipe is given by:
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