To raise $1000, 1000/2=500 bars must be sold by 150 students (between them). 500/150=10/3=3⅓. If each student sold 3 bars, then this would raise 3×150×2=$900, insufficient to meet the goal. But if each student sold 4 bars they would raise $1200. If 3 students sold 10 bars between them as a group, 50 groups would raise $1000. On average, the number of bars is 3⅓ for each student.