Question 1043553: The mean of nine test scores is 61. If a score of 71 is added to the group of scores, what is the new mean?
Found 2 solutions by Boreal, jim_thompson5910:
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! mean=total/number
61=total/9
total=9*61=549
add 71 to it and get 620.
now mean is 620/10=62.
This makes sense, because the score of 71 is higher than the mean, so the mean should rise, and indeed, it rises by exactly 1, because 71 is 10 more than 61 and there are 10 in the group now.
Answer by jim_thompson5910(35256)  (Show Source):
You can put this solution on YOUR website! Let
S = sum of the nine test scores
Dividing the sum (S) by 9 gives the mean of 61, so,
S/9 = 61
Solve for S. Do this by multiplying both sides by 9
S/9 = 61
(S/9)*9 = 61*9
S = 549
So we know that the sum of the nine scores is 549. We don't know the actual individual scores. However, we can determine the new mean.
Add 71 to the sum of the other scores (549) to get
71+549 = 620
Now divide this by 10 to compute the mean of the 10 scores
620/10 = 62
So the mean has gone from 61 to 62
The final answer is 62
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