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If for some x ∈ R, the frequency distribution of the marks obtained by 20 students in a test is : Marks 2 3 5 7 Frequency (x + 1) 2 2x – 5 x 2 – 3x x then the mean of the marks is

1. 3.0
2. 2.8
3. 2.5
4. 3.2

Correct answer: 2.8

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