1. describe a mandolin. describe its appearance, its construction, its sound, and how it is used musically.

Mandolin is a stringed musical instrument resembling a guitar. They were used as solo and accompaniment instruments, often also as the upper choir of lute and later guitar orchestras.  

The mandolin is tuned in the same way as the violin. The strings are doubled. It has a strong piercing sound and plays accompaniments, such as punches for the second time or slashing. Ornaments such as tremolo or solo strum are also used. Nowadays, playing mandolin is becoming more widespread, especially in bluegrass, otherwise rarely in folk or rock.  

Mandolin is a practical musical instrument. Its small size is an advantage on the road and during the musical play itself. However, it can be a problem for people with big and strong fingers, and it may become a bit difficult to play a narrow fingerboard.

including the octave, the answer would 8 notes in a major scale with one note being played twice. ex) c major scale includes: c, d, e, f, g, a, b, c

notice that c is played twice

however, if you were to ask me how many different notes are in a major scale- the answer would be 7.