Question

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

Answer 1

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.