Assertion: piano's key | /r/HasProperty | 21 units wide
Facets:
Source sentences:
text: If the internal spacing for the internals of a piano or organ is perfect, giving each of the twelve notes of the octave twelve units of width on the keyboard, then the three white keys for C, D, and E would be 20 units wide, while the white keys for F, G, A, and B would be 21 units wide.