11. Following is the distribution of marks obtained by 60 students: Calculate the arithmetic mean

MarksMorethan 0more than 10More than20More than 30More than 40More than 50No ofstudents60564020103

xThe table can be given as, 
 
More than Cumulative frequency Class frequency(fi) fi.xi
More than 0 60 0-10 4 20
More than 10 56 10-20 16 240
More than 20 40 20-30 20 500
More than 30 20 30-40 10 350
More than 40 10 40-50 7 315
More than 50 3 50-60 3 165

Now using direct method for finding the mean of 60 student, 

Mean = fi xifi159060=26.5

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