Q3 of 141 Page 7

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


Let the assumed mean (A) = 4













































No. of branches (xi)



No. of plants (fi)



ui = xi - A = xi - 4



fiui



2



49



-2



-98



3



43



-1



-43



4



57



0



0



5



38



1



38



6



13



2



26




N = 200




∑fiui = -77



Average number of branches per plant = A +


= 4 + =


= 3.62 (approx.)


More from this chapter

All 141 →
1

The number of telephone calls received at an exchange per interval for 250 successive one-minute intervals are given in the following frequency table.























No. of calls (x):



0



1



2



3



4



5



6



No. of intervals (f):



15



24



29



46



54



43



39



Compute the mean number of calls per interval.

 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


 4

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.

 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.