Answer:
Below in bold.
Explanation:
3.1.
In ascending order:
18 20 36 36 45 48 51 54 77 81
3.2
Mean =sum / 10 =
466/10
= 46.6.
Range = 81 - 18 = 63.
3.4
Mode = 36. ( mode is most frequent occurring mark)
3.5.
24 + A + 21 = 3* 20
A = 60 - 24 - 21
= 15.