From an iq test online I have trouble doing the problem:
357, 1251, 152, ?, ?, 0
I tried a common trick to ignore the spaces and add commas elsewhere but it doesn't do anything.
The answer is
Does anyone know why?
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The leading zero that got edited out is definitely relevant, the puzzle won't work without it.
You get the next number by
taking the first digit of the previous number, multiplying it by each of the other digits in turn, and writing the results together, backwards.
For example, to get from 357 to 1251,
3*5, 3*7 (multiply first digit with all others) 15 21 (read backwards) 1251