Multiple choice general knowledge math & puzzles

Certain money doubles itself according to compound interest in 3 years. How much time it takes to become 4 times?

  1. 10 years

  2. 6 years

  3. 2 years

  4. 8 years

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

If money doubles in 3 years under compound interest, then doubling again takes another 3 years, giving 4 times the original in 6 years total. Mathematically, if (1+r)^3 = 2, then (1+r)^6 = 4, confirming 6 years.