A new cookbook is becoming popular. The local bookstore ordered 72 copies in October, 63 copies in November, 54 copies in December, and 45 copies in January. What kind of sequence is this?

Answer 1

The number of copies ordered each month forms the following sequence:

• October: 72 copies
• November: 63 copies
• December: 54 copies
• January: 45 copies

To determine the type of sequence, we can look at the differences between consecutive terms:

• From October to November: 72 - 63 = 9
• From November to December: 63 - 54 = 9
• From December to January: 54 - 45 = 9

The difference between each consecutive month is consistently 9. Since the difference is constant, this sequence is an arithmetic sequence (or arithmetic progression) with a common difference of -9.