| Marks | 2 | 3 | 5 | 7 |
| Frequency | \[{{(x+1)}^{2}}\] | \[2x-5\] | \[{{x}^{2}}-3x\] | \[x\] |
| then the mean of the marks is : |
A) 2.8
B) 3.2
C) 3.0
D) 2.5
Correct Answer: A
Solution :
\[\sum\limits_{{}}^{{}}{{{f}_{i}}}=20=2{{x}^{2}}+2x-4\] \[\Rightarrow {{x}^{2}}+2x-24=0\] \[x=3,-4\](rejected) \[\bar{x}=\frac{\sum\limits_{{}}^{{}}{{{x}_{i}}{{f}_{i}}}}{\sum\limits_{{}}^{{}}{{{f}_{i}}}}=2.8\]
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