Answer:
77.3
Step-by-step explanation:
Recall that the arithmetic mean is found as follows:
sum of all data
a. m. = ---------------------------
number of data
sum
The mean score of 27 test results is thus 78 = --------
27
Note that we can find the sum of all 27 of the original scores by multiplying 78 by 27: 2106.
Now we include two more scores. Instead of the original sum, 2106, we have
2106 + 69 + 66
a. mean = ---------------------------
29
which comes out to 2241/29 = 77.3
