Multiple choice

3, 12, 48, 192, 768………….. The first five terms in a sequence are shown above. Each term after the first is found by multiplying the term immediately preceding it by 4. Which term in this sequence is equal to 3.420?

  1. 18th

  2. 19th

  3. 20th

  4. 21st

  5. 22nd
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The sequence is 3 * 4^0, 3 * 4^1, 3 * 4^2, ... The n-th term is 3 * 4^(n-1). We want 3 * 4^(n-1) = 3 * 4^20. Thus, n-1 = 20, so n = 21.

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