Form a sequence that has two arithmetic means between -13 and 89. a. -13, 33, 43, 89 c. -13, 21, 55, 89 b. -18, -36, -72, -144 d. -18, -81, -144
Solution:
Since it has to be between -13 and 89, letter d and b are not anymore considered to be the answer.
for a:
33-(-13)=46=d
43-33=10=d the value for this d is different from the two sequence,
89-43=46=d
they have different value for d, thus this is not the answer!
for c:
21-(-13)=34=d
55-21=34=d
89-55=34=d
they have the same value for d, thus the correct answer is c. -13, 21, 55, 89