Question

Identify a pattern in each list of numbers. Then use this pattern to find the next

number.
-1215, 405, -135, 45, -15,

Answer 1

• pattern: common ratio of -1/3
• next: 5

Explanation:

When looking for patterns in a sequence, it is useful to look at differences, ratios, and differences of differences. Here, the terms have a common ratio:

405/-1215 = -135/405 = 45/-135 = -15/45 = -1/3

__

For this sequence, each number is -1/3 times the previous number.

The next number is (-15)(-1/3) = 5.