Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
1969 South Korean constitutional referendum
Table title:
Results
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Choice </th><th colspan=1 rowspan=1 > Votes </th><th colspan=1 rowspan=1 > % </th></tr>
<tr> <td colspan=1 rowspan=1 > For </td><td colspan=1 rowspan=1 > 7,553,655 </td><td class="highlighted"  colspan=1 rowspan=1 > 67.5 </td></tr>
<tr> <td colspan=1 rowspan=1 > Against </td><td colspan=1 rowspan=1 > 3,636,369 </td><td colspan=1 rowspan=1 > 32.5 </td></tr>
<tr> <td colspan=1 rowspan=1 > Invalid/blank votes </td><td colspan=1 rowspan=1 > 414,014 </td><td colspan=1 rowspan=1 > – </td></tr>
<tr> <td colspan=1 rowspan=1 > Total </td><td colspan=1 rowspan=1 > 11,604,038 </td><td colspan=1 rowspan=1 > 100 </td></tr>
<tr> <td colspan=1 rowspan=1 > Registered voters/turnout </td><td colspan=1 rowspan=1 > 15,048,925 </td><td class="highlighted"  colspan=1 rowspan=1 > 77.1 </td></tr>
<tr> <td colspan=3 rowspan=1 > Source: Nohlen et al. </td></tr>
</table>
Question:
What percentage of voters, with a turn out of 77.1% approved the changes to the 1969 South Korean constitution?
Answer:
The changes to the 1969 South Korean constitution were approved by 67.5% of voters, with a turnout of 77.1%.