GMAT Quantitative Reasoning Practice Test 5

The number we're supposed to see in the answers is $4\times 3\times 2=24$. It fits all answers.
The real question is the decimal of the answer; the basic rule is to add the decimals $2+2+1=5$.
We want the answer in percent terms so we need to take two decimals down, overall -3 .
The answer is $24∕1000$ ( 3 decimals) $=0.024\%$