Mean of a frequency table

This type of question, asked 3 times: CDS 1 2023, CDS 2 2025, CDS 2 2026. All 3 questions below, oldest first.

Try each one first, then open its answer.

Question 1 (case study, 2 parts)
CDS 1 2023
Consider the following data for the next two (02) items that follow :
Class 40 - 50 50 - 60 60 - 70 70 - 80
Frequency 4 3 1 2
83 $What is the mean of the distribution ?$
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84 $If M is the median, then what is the value of 3M ?$
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Question 2
CDS 2 2025
93 $The frequency distribution of marks of 100 candidates in a particular examination is as follows : Marks Number of Candidates More than 10 100 More than 20 75 More than 30 60 More than 40 40 What are the average marks of the candidates?$
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Question 3
CDS 2 2026
98 $Consider the following discrete grouped data : x f 1261481010169183 What is the arithmetic mean of the above distribution ?$
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Question 1 (case study, 2 parts)