Math Problem Statement
Solution
The question in the image asks about a frequency distribution of marks obtained by 120 students. The goal is to find the missing frequencies and , given that the mean of the marks is 59. Here's a breakdown of the problem:
Frequency Distribution Table:
Marks Interval | No. of Students (Frequency) |
---|---|
0-10 | 1 |
10-20 | 3 |
20-30 | 7 |
30-40 | 15 |
40-50 | |
50-60 | 9 |
60-70 | 27 |
70-80 | 18 |
80-90 | |
90-100 | 4 |
Given:
- Total number of students: 120
- Mean marks: 59
Steps to Solve:
-
Calculate the assumed mean and class intervals: We will use the formula for the mean of a grouped frequency distribution:
where:
- = frequency of the class
- = midpoint of the class intervals
The midpoints of the class intervals can be calculated as:
So, for each class interval, the midpoints are:
-
Set up the equation for the mean: We know the mean is given as 59, and the sum of frequencies (i.e., total number of students) is 120. So, the equation becomes:
Substituting known values, we can form an equation in terms of and .
-
Calculate the total number of students: From the frequencies, the sum of the known frequencies is:
Since the total number of students is 120, we can deduce that:
-
Form the equation for the mean: Using the midpoints and frequencies, the equation for the sum of the products of midpoints and frequencies will be:
Simplify this equation, and use the given mean (59) to solve for and .
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Math Problem Analysis
Mathematical Concepts
Statistics
Mean of grouped data
Frequency distribution
Formulas
Mean of grouped data formula: Mean = (Σf_i * x_i) / Σf_i
Midpoint of class interval: (Lower limit + Upper limit) / 2
Theorems
-
Suitable Grade Level
Grades 10-12
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