The Perfect Fifth of a String

The whole string gives us the original no. And the two halves vibrating separately, give us the same not and octave. If you open like a real piano, you can see that with the naked eye,. So the first overtone of this b, 30 hurts, is 60 hurts. Vibrates at 60 hurts. What not is that? Sab and the same beb, b, ad, an octava.