The mean score on a set of 27 tests is 78. suppose two more students take the test and score 69 and 66. what is the new mean?

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