Students enrolled in Science are not allowed to take either Economics or Political Science, while students enrolled in Arts are not allowed to take either Physics or Mathematics.
Recently, the college has started a third specialization called MatEco that requires students to take Economics and Mathematics. However, MatEco students would not be allowed to take either Physics or Political Science. When the college opens this new specialization for enrolment, it allows students, originally enrolled in Science or Arts, to switch to MatEco.
From among the students originally enrolled in Arts, 20 students switch to MatEco. This makes the number of Science students twice the number of Arts students. After this, from among the students who originally enrolled in Science, 45 students switch to MatEco. This makes the number of Arts students twice the number of Science students.
In total, how many students, from among those originally enrolled in Science or Arts, are now taking Economics?
D
Step-by-Step Solution
Key idea: This is a set theory and algebraic translation problem, recognizable by the shifting of students between distinct groups and the resulting ratio changes.
Step 1: Let the initial number of Science students be and Arts students be .
Step 2: 20 students switch from Arts to MatEco. The remaining Arts students are . Science remains .
Step 3: The problem states Science is now twice Arts: .
Step 4: Next, 45 students switch from Science to MatEco. The remaining Science students are . Arts remains .
Step 5: The problem states Arts is now twice Science: .
Step 6: Substitute from Step 3 into Step 5: .
Step 7: Find : .
Step 8: We need the total number of students originally in Science or Arts who are NOW taking Economics.
Step 9: Originally, only Arts students took Economics. Science students did not.
Step 10: After the switches, the students taking Economics are the remaining Arts students and ALL MatEco students (since MatEco requires Economics).
Step 11: Remaining Arts = . Total MatEco = .
Step 12: Total taking Economics = .
Answer: 95