Final answer:
To determine the number of 8th graders at Jefferson Middle School, calculate the counts for 7th and 6th graders based on given ratios (5/12 and 1/4 of total students, respectively) and subtract from the total number of students. The calculation yields 108 students are in the 8th grade.
Step-by-step explanation:
Let's calculate the number of Jefferson Middle School students in each grade. To find out how many 7th graders there are, we multiply the total number of students, 324, by 5/12, since 5/12 of the students are in 7th grade:
Number of 7th graders = 324 × (5/12) = 135
Next, we find out how many 6th graders there are by multiplying the total number by 1/4, as 1/4 of the students are in 6th grade:
Number of 6th graders = 324 × (1/4) = 81
To find out how many 8th graders there are, we subtract the number of 6th and 7th graders from the total number of students:
Number of 8th graders = Total students - (Number of 7th graders + Number of 6th graders)
= 324 - (135 + 81) = 324 - 216 = 108
Therefore, there are 108 students who are 8th graders at Jefferson Middle School.