When working with percentages of numbers multiples of 10, is faster to work with multiples of 10% or 1%. That means that for example if a question asks you for the 40% of a quantity is better to divide that quantity by 10 and the multiplying it by 4, same if is 50,60,20 percent. It's the same than multiplying by 0.4 but working with decimals is usually slower.

In this problem, we have a total of 4400 participants. They tell you that there's an x percent that can be rounded to 8, so inmediately we can assume that the value of the percentage is between 7.5 and 8.5 percent, not including the 8.5.

So how to to obtain 7.5 and 8.5 percent of the total without using decimals?

We apply the technic mentioned before, working in units of 1 percent taking advantage of the two last digits of the total of participants that are 0.
7.5 percent is 0.5 less than 8 percent.
8.5 percent is 0.5 more than 8 percent.
And 8 percent is 8 times 1 percent.

1 percent is 4400/100= 44
So 0.5 percent is 22.

Thus
8 percent is 8*44, that is equal to 352

7.5 percent = 352-22=330 (included)
8.5 percent = 352+22=374 (not included)

So the only options that are between this numbers are 330 and 352

I know that it seems like a long proccess but when you get used to it, you'll see how fast it is.