Find the mean of the following distribution :
Class 30 – 40 40 – 50 50 – 60 60 – 70 70 – 80
Frequency 6 13 8 12 11
calculate class mark, mid value or mid -x [x] then the product f*x
Class f x f*x
30-40 6 35 210
40-50 13 45 585
50-60 8 55 440
60-70 12 65 780
70-80 11 75 825
Total Σf =50, Σfx= 2840
Mean = Σfx / Σf = 2840 / 50 = 56.8
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statistics arithmetic mean by direct method
cbse 10th maths previous years question papers 2025 2026 question in statistics
