Think of this as taking three copies of eight. The word of is frequently used to mean multiplication when we're talking about fractions or percents. One-fourth of seven is , while 25 percent of two hundred is 0.25 × 200. John Mayer's "Half of My Heart" is .
, while 25 percent of two hundred is 0.25 × 200. John Mayer's "Half of My Heart" is 
.