how many sharps are used in the song in key of G?

1 is in G-sharp major, although the key signature has four sharps.

Where are the notes placed on a music?

staff

Appropriate music symbols, depending upon the intended effect, are placed on the staff according to their corresponding pitch or function. Musical notes are placed by pitch, percussion notes are placed by instrument, and rests and other symbols are placed by convention.

how many sharps are used in the song in key of G?

G major has one sharp

where are the notes placed on a music?

music symbols are placed on staff