Multiple choice general knowledge math & puzzles

The least number of complete years in which a sum of money put out at 20% compound interest will be more than doubled is:

  1. 3

  2. 4

  3. 5

  4. 6

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

At 20% compound interest, we need the smallest integer n where (1.20)^n > 2. Checking: n=1: 1.20, n=2: 1.44, n=3: 1.728, n=4: 2.0736. Since 2.0736 > 2, the answer is 4 years. Option B is correct.