Multiple choice general knowledge math & puzzles

What 5-digit number has the following property? If we put numeral 1 in front of the number, we get a number three times smaller, than if we put the numeral 1 behind this number.

  1. 32567

  2. 42859

  3. 42857

  4. 42569

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

If the number is x, then 100000 + x is the number with 1 in front, and 10x + 1 is the number with 1 behind. The equation is 3(100000 + x) = 10x + 1. Solving gives 7x = 299999, so x = 42857.