okay--this is easy--but i keep getting a different answer than what the teacher has given--what am i doing wrong?
12 is one half percent of what number--
he said it's 2400--
your teacher is correct, who would have thunk it, right?
recall that "percentage" means "out of 100" or "divided by 100." so saying 1/2 percent is the same as saying $\displaystyle \frac {\frac {1}{2}}{100} = \frac {1}{200}$
also, in math, "of" means "multiply." so saying "1/2 percent of" means "$\displaystyle \frac {1}{200} \times$"
So let the number be $\displaystyle x$
since 12 is 1/2 percent of $\displaystyle x$, we have:
$\displaystyle 12 = \frac {1}{200}x$
$\displaystyle \Rightarrow x = 200(12) = 2400$
I would think of it like this.
12 = 1/2%
24 = 1%
Now you have an easier number to work with.
1% x 100 = 100%
24 x 100 = 2400
I just work it out like that, though it may prove time consuming with more difficult questions. Just do the same to the left had side as to the right. I know your question has already been answered, but I tried to explain it in a different way.