<PRE><B>Question 393494</B>
&lt;br&gt;&lt;font face=&quot;Tahoma&quot;&gt;We are looking at a total of 50 keys. &lt;br&gt;

They tell us to subtract 1 from that total, and divide by 7.&lt;br&gt;

{{{50-1=49}}}&lt;br&gt;

{{{49/7=7}}}&lt;br&gt;

Thus, there should be 7 complete octaves on a piano with 50 keys.&lt;br&gt;

It is easier to see this if you try to start from the beginning.&lt;br&gt;

8 keys = 1 complete octave  {{{8-1=7}}} {{{7/7=1}}}&lt;br&gt;

15 keys = 2 complete octaves  {{{15-1=14}}} {{{14/7=2}}}&lt;br&gt;

22 keys = 3 complete octaves  {{{22-1=21}}} {{{21/7=3}}}&lt;br&gt;

And so on....&lt;br&gt;

The reason this works the way it does is because the 8th key is not only the last key in the first octave, it is the first key in the second octave!&lt;br&gt;

I hope this helps!&lt;br&gt;</PRE>