Q9 of 141 Page 8

The following table gives the number of boys of a particular age in a class of 40 students. Calculate the mean age of the students.





















Age (in year):



15



16



17



18



19



20



No. of students:



3



8



10



10



5



4












































Age (x)



No. of students (y)



yx



15



3



45



16



8



128



17



10



170



18



10



180



19



5



95



20



4



80




N = 40



∑yx = 698



Mean =


= = 17.45


Therefore, mean age is 17.45 years.


More from this chapter

All 141 →
7

Find the missing frequency (p) for the following distribution whose mean is 7.68.





















x:



3



5



7



9



11



13



y:



6



8



15



p



8



4


 8

Find the value of p, if the mean of the following distribution is 20.



















x:



15



17



19



20+p



23



y:



2



3



4



5p



6


 10

Candidates of four schools appear in a mathematics test. The data were as follows:




























Schools



No. of Candidates



Average Score



I



60



75



II



48



80



III



Not available



55



IV



40



50



If the average score of the candidates of all the four schools is 66, find the number of candidates that appeared from school III.

 11

Five coins were simultaneously tossed 1000 times and at each toss the numbers of heads were 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 per toss



No. of tosses



0



38



1



144



2



342



3



287



4



164



5



25



Total



1000