Further Mathematics Paper 2, WASSCE (PC), 2017

      Question 6:

      The table shows the heights in cm of some seedlings in a certain garden.

 

Ages (years)

 

15 – 18

 

19 – 22

 

23 – 26

 

27 – 30

 

31 - 34

 

35 – 38

Frequency

40

33

25

10

8

4

 

Using an assumed mean of 24.5, calculate the mean of the distribution.

Observation

 

The Chief Examiner reported that this question was very popular among the candidates.  They also performed very well.  They presented the frequency table as follows:

 

Ages (years)

 

Frequency (f)

Midpoint
 (x)

d = (x – 24.5)

fd

15 – 18

40

16.5

-8

-320

19 – 22

33

20.5

-4

-132

23 – 26

25

       2. 45

           0

0

27 – 30

10

28.5

4

40

31 – 34

8

32.5

8

64

35 – 38

4

36.5

12

48

 

 = 120

 

 

 = -300

Mean = 24.5 -  = 24.5 – 2.5 = 22.