The mean of the following frequency distribution is 25.2. Find the missing frequency x. Class
0 - 10
10 - 20
20 – 30
30 – 40
40 - 50

Frequency
8
x
10
11
9

Solution:-

Frequency Distribution     Frequency     Mid values     F*M

0 - 10                                    8                     5                40

10 - 20                                  x                    15               15x

20 - 30                                 10                   25               250

30 - 40                                 11                   35               385

40 - 50                                  9                    45               405

                                         Σf = 38+x                      Σfm = 1080+15x

Given Mean = 25.2

Mean = Σfm/Σf

25.2 = 1080+15x/38+x

25.2 × (38+x) = 1080+15x

957.6+25.2x = 1080+15x

25.2x - 15x = 1080 - 957.6

10.2x = 122.4

x = 122.4/10.2

x = 12

Missing frequency = 12  Answer

the inequality is:

250c+180g≥950

step-by-step explanation:

let c denotes the number of days in a week   miyoko worked as a cryptographer.

and g denotes the number of days in a week she works as a geologist.

now we are given that she earns $250 for every day she works as a cryptographer,and earns $180 for every day she works as a geologist.

now miyoko's goal is to earn more than $950 this week.

hence, the inequality could be represented as:

250c+180g≥950