9th: 20% 10th: 40% 11th: 30% 12th: 10% the students in four grades in the toptalent high school are shown above. if the difference between the total number of students in 11th and 12th grade and the total number of students in the 9th and 10th grade is 100, how many students are there at the school?

The total of students in 11th and 12th grade is 30% + 10% = 40% of the students at the school.

The total of students in the 9th and 10th grade is 20% + 40% = 60% of the students at the school.

The difference between the groups is 60% - 40% = 20% of the students at the school. That difference is 100 students, so 20% of the student body is 100 students. Multiplying by 5 tells us 100% of the student body is 500 students.

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