answer is 4.
Explanation:
Mean is found by taking the sum of the values and dividing by the count.
When looking at all 6 numbers, the mean is:
4.5
=
sum of 6 values
6
⇒
sum of 6 values
=
27
When looking at the 2 values with a mean of 5.5:
5.5
=
sum of 2 values
2
⇒
sum of 2 values
=
11
Which means the mean of the 4 values is:
mean
=
27
−
11
4
=
16
4
=
4
