Complete the series 2, 6, 18, …, 486. What is the 4th term from the last?

Correct answer: 18. Each term is multiplied by 3: 2, 6, 18, 54, 162, 486. The 4th from the last is 18.

Background: A series where each term is multiplied by the same number is a geometric progression.

• 20: 20 is not in the series.
• 22: 22 is not in the series.
• 19: 19 is not in the series.

Did you know? To count from the end, write all terms first.

Memory trick: × 3 each time.