Q4 of 141 Page 7

The following table gives the number of children of 150 families in a village





















No. of children (x):



0



1



2



3



4



5



No. of families (f):



10



21



55



42



15



7



Find the average number of children per family.

Let the assumed mean (A) = 2



















































No. of children (xi)



No. of families (fi)



ui = xi – A = xi - 2



fiui



0



10



-2



-20



1



21



-1



-21



2



55



0



0



3



42



1



42



4



15



2



30



5



7



3



21




N = 150




∑fiui = 52



Average number of children per family = A +


= 2 + =


= 2.35 (approx)


More from this chapter

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2

Five coins were simultaneously tossed 1000 times, and at each toss the number of heads was observed. The number of tosses during which 0, 1, 2, 3, 4 and 5 heads were obtained are shown in the table below. Find the mean number of heads per toss





















No. of heads pre toss(x):



0



1



2



3



4



5



No. of tosses (f):



38



144



342



287



164



25


 3

The following table gives the number of branches and number of plants in the garden of a school.



















No. of branches (x):



2



3



4



5



6



No. of plants (f):



49



43



57



38



13


 5

The marks obtained out of 50, by 102 students in a Physics test are given in the frequency table below:



























Marks (x):



15



20



22



24



25



30



33



38



45



Frequency (f):



5



8



11



20



23



18



13



3



1



Find the average number of marks.

 6

The number of students absent in a class were recorded every day for 120 days and the information is given in the following frequency table:

























No. of students absent (x):



0



1



2



3



4



5



6



7



No. of days (f):



1



4



10



50



34



15



4



2



Find the mean number of students absent per day.