Final answer:
The students in the fifth grade sold 171 erasers, by dividing the total erasers sold by the fourth graders (684) by 4.
Step-by-step explanation:
The question asks us to determine how many erasers the fifth grade students sold based on the information that fourth grade students sold four times as many. First, we know the total number of erasers sold by the fourth graders, which is 684 erasers. Since the fifth grade students sold a quarter of that amount, we simply divide by 4.
To find the number of erasers sold by the fifth grade students:
684 erasers ÷ 4 = 171 erasers.
Therefore, the students in the fifth grade sold 171 erasers for the fund-raiser.