Find the four arithmetic means between - 21 and - 36.

The numbers given in the problem above are part of an arithmetic sequence with first and sixth terms equal to - 21 and - 36, respectively. Firstly, calculate for the common difference (d).

d = (-36 - - 21) / (6 - 1) = - 3

The arithmetic mean is calculated by adding - 3 to the term prior to it.

a2 = - 21 + - 3 = - 24 a3 = - 24 + - 3 = - 27

a4 = - 27 + - 3 = - 30 a5 = - 30 + - 3 = - 33

Thus the four arithmetic means are - 24, - 27, - 30, and - 33.