All of the students who took chemistry at Groveton High School last year were juniors or seniors, as shown in the table below. If 80% of the students who took chemistry passed, then what fraction of the students in the combined junior and senior classes took chemistry?
Class Total # of Students in Class # of Students who passed
Junior 80 42
Senior 70 30
The correct answer is 3/5, but I don't know how. Thank you!
72 students passed so
72/0.8 = 90
90/150 can be simplified to 3/5
Check my thinking
To find the fraction of students in the combined junior and senior classes who took chemistry, we need to calculate the total number of chemistry students and the total number of junior and senior students.
For the junior class:
Total number of students who took chemistry in the junior class = 42
Total number of students in the junior class = 80
For the senior class:
Total number of students who took chemistry in the senior class = 30
Total number of students in the senior class = 70
Adding the number of students who took chemistry in both classes:
Total number of students who took chemistry = 42 + 30 = 72
Adding the total number of students in both classes:
Total number of students = 80 + 70 = 150
Therefore, the fraction of students in the combined junior and senior classes who took chemistry is:
Fraction = Total number of students who took chemistry / Total number of students
Fraction = 72 / 150
The fraction is 0.48 or 48/100.
To find the fraction of students in the combined junior and senior classes who took chemistry, you first need to calculate the total number of students who took chemistry.
For the junior class, the number of students who took chemistry can be found by subtracting the number of students who passed from the total number of students: 80 - 42 = 38.
For the senior class, the number of students who took chemistry can be found in the same way: 70 - 30 = 40.
To get the total number of students who took chemistry, add the number of students from the junior class to the number of students from the senior class: 38 + 40 = 78.
Now, you have the total number of students who took chemistry, which is 78.
To find the fraction of students in the combined junior and senior classes who took chemistry, divide the total number of students who took chemistry by the sum of the total number of students in the junior and senior classes:
78 / (80 + 70) = 78 / 150 = 0.52
Therefore, the fraction of the students in the combined junior and senior classes who took chemistry is 0.52.