Algebra-1

Question Analysis
This question involves a two-way frequency table with variables "grade" (11th/12th) and "music activity" (choir/band).
The main focus is on calculating the column marginal frequency for "Choir" using the total number of students.

Key Concept Explanation
Total Marginal Frequency: The sum of all row marginal frequencies (or column marginal frequencies) equals the total number of observations in the table.
For columns: Total students = marginal frequency (Choir) + marginal frequency (Band).

Step-by-Step Solution
Identify the total number of students, which is the grand total in the table: 140.
The marginal frequency for "Band" is given as 80.
Let the marginal frequency for "Choir" be y.
Using the total relationship: .
Solve for y: