WAEC 2023 · Paper 1 · Q16

The table shows the marks obtained by students in a test.

Marks	1	2	3	4	5
Frequency	2	$k$	1	1	2

If the mean mark is 3, find the value of $k$ .

Worked solution (try it first)

The total frequency is $2 + k + 1 + 1 + 2 = 6 + k$ .
The total of the marks is $2(1) + 2k + 3 + 4 + 2(5) = 19 + 2k$ .
Mean is total over frequency: $\dfrac{19 + 2k}{6 + k} = 3$ , so $19 + 2k = 18 + 3k$ .
So $k = 1$ , option A.