The marks obtained by a group of students in a class test are shown below.

Given the mean of the marks is 6.5, find the value of k.

$\frac{{5 \times 6 + 6k + 7 \times 3 + 8 \times 1 + 9 \times 2 + 10 \times 1}}{{13 + k}} = 6.5$ (or equivalent)     (M1)(A1)(A1)

Note: Award (M1)(A1) for correct numerator, and (A1) for correct denominator.

$0.5k = 2.5 \Rightarrow k = 5$     A1

[4 marks]

The question was well done generally as one would expect.