Question

Q3. The following distribution shows the daily pocket allowance of children of a locality. The mean pocket
allowance is 18. Find the missing frequency f.
Daily pocket
11-13 13-15
15-17 17-19 19-21 21-23 23-25
Number of children
7
6
9
13
f
5
4

need step by step explanation...plz help me ​

Answer 1

Answer:

20

Step-by-step explanation:

mean of 11-13 is 12 --have frequency 7

mean of 13-15 is 14   --have frequency 6

mean of 15-17 is 16   --have frequency 9  

mean of 17-19 is 18  --have frequency 13

mean of 19-21 is 20  have frequency f

 mean of 21-23 is 22   --have frequency 5

mean of 23-25 is 24  --have frequency 4

therefore using formula : mean=$\frac{total pocket money }{total children}$

$18=\frac{(7*12) + (6*14)+(9*16)+(13*18)+(f*20)+(5*22)+(4*24)}{7+6+9+13+f+5+4}$

$18*(44+f)=752+20f$

$792+18f=752+20f$

⇒$2f=40$

⇒$f=20$