Explanation:
0.5(-77.8 - 11)/-4 =
= 0.5(-88.8)/-4 = 0.5(22.2) = 11.1
as you can see, when just doing it step by step, this can be done just in the head without the need of a calculator.
remember the priorities for mathematical operations :
1. brackets
2. exponents
3. multiplications and divisions
4. additions and subtractions
and also
+×+ = +
-×- = +
-×+ = -
+×- = -
therefore, -88.8/-4 = 22.2
and
0.5 = 1/2
so, 22.2×0.5 = 22.2/2 = 11.1
regarding average :
the average of a set of data is always the sum of all the data divided by the number of data points.
so, we see here 5 data points.
their sum is
-32.6 + 24.7 - 8.3 + 19.1 - 8.4 = -5.5
the average is then
-5.5/5 = -1.1 m sea level