Question 62479
Question 1
{{{Mean = Sum of scores / Number of scores}}}

You know the number of scores (count them to get 7) and you know the mean is 9.

Rearrange the formula to find the sum of the scores
{{{Sum of scores = Mean * Number of scores}}} Substitute the Mean and number of scores into the formula to find the sum of the scores.
{{{Sum of scores = 9 * 7 = 63}}} Summing 8,18,18,3,6,3 gives a total of 56 so the missing number must be 7.


Question 2
The Range is found by subtracting the smallest number from the largest. In this case you have two alternatives; n may be the smallest number in the set or the largest.

If n is the smallest then it would be 3 as 17 - 3 = 14. The mean would be 39 / 6 = 6.5
If n is the largest then it would be 18 as 18 - 4 = 14. The mean would be 54 / 6 = 9