Middle School

Determine whether each sequence is arithmetic, geometric, or neither:

1. 98.3, 94.1, 89.9, 85.7
2. 1, 0, -1, 0
3. 1.75, 3.5, 7, 14
4. -12, -10.8, -9.6, -8.4
5. -1, 1, -1, 1

Answer :

The given sequences vary in their patterns, with the first, fourth being arithmetic, the third being geometric, and the second, fifth sequences being neither arithmetic nor geometric.

To determine if the sequences are arithmetic, geometric, or neither, we need to look for a common difference or ratio between terms. Let's analyze each given sequence:

  1. 98.3, 94.1, 89.9, 85.7: Subtract each term from the one that follows to check for an arithmetic sequence. The differences are -4.2, -4.2, -4.2, which are consistent, indicating an arithmetic sequence.
  2. 1, 0, -1, 0: The differences/ratios between terms are not consistent, so it is neither arithmetic nor geometric.
  3. 1.75, 3.5, 7, 14: Each term is multiplied by 2 to get the next. This is a common ratio, indicating a geometric sequence.
  4. -12, -10.8, -9.6, -8.4: Adding 1.2 to each term gets the next term, indicating an arithmetic sequence with a common difference of 1.2.
  5. -1, 1, -1, 1: There is no common difference or common ratio, so this sequence is neither arithmetic nor geometric.