Question

the mean of the following distribution is 18 find the class 19 -21 class/frequency11-13/3 13-15/6 15-17/917-19/13 19-21/f 21-23/5 23-25/4

Answer 1

Solution the value of f is 8

Answer 2

Answer:

The frequency in the class 19-21 is 86.

Step-by-step explanation:

Given : The mean of the following distribution is 18.

To find : The class 19 -21 frequency or value of f?

Solution :

We create the table first

 Class      Frequency

  11-13               3

  13-15              6

  15-17              9

  17-19              13

  19-21              f

  21-23              5

  23-25             4

Number of frequency is 7

Mean is the total frequency divided by number of frequency.

$\text{Mean}=\frac{\text{sum of frequency}}{\text{number of frequency}}$

$18=\frac{3+6+9+13+f+5+4}{7}$

$18\times 7=40+f$

$126-40=f$

$86=f$

Therefore, The frequency in the class 19-21 is 86.