To divide fractions, invert the second fraction and then multiply:

\( \frac{3}{9} \) ÷ \( \frac{4}{9} \) = \( \frac{3}{9} \) x \( \frac{9}{4} \)

To multiply fractions, multiply the numerators together and then multiply the denominators together:

\( \frac{3}{9} \) x \( \frac{9}{4} \) = \( \frac{3 x 9}{9 x 4} \) = \( \frac{27}{36} \) = \(\frac{3}{4}\)

To multiply fractions, multiply the numerators together and then multiply the denominators together:

\( \frac{1}{6} \) x \( \frac{4}{7} \) = \( \frac{1 x 4}{6 x 7} \) = \( \frac{4}{42} \) = \(\frac{2}{21}\)

To take the square root of a fraction, break the fraction into two separate roots then calculate the square root of the numerator and denominator separately:

\( \sqrt{\frac{4}{64}} \)
\( \frac{\sqrt{4}}{\sqrt{64}} \)
\( \frac{\sqrt{2^2}}{\sqrt{8^2}} \)
\(\frac{1}{4}\)

The first few multiples of 2 are [2, 4, 6, 8, 10, 12, 14, 16, 18, 20] and the first few multiples of 6 are [6, 12, 18, 24, 30, 36, 42, 48, 54, 60]. The first few multiples they share are [6, 12, 18, 24, 30] making 6 the smallest multiple 2 and 6 have in common.

In order to find how many additional workers are needed to staff the extra crews you first need to calculate how many workers are on a crew. There are 8 workers at the company now and that's enough to staff 4 crews so there are \( \frac{8}{4} \) = 2 workers on a crew. 9 crews are needed for the busy season which, at 2 workers per crew, means that the roofing company will need 9 x 2 = 18 total workers to staff the crews during the busy season. The company already employs 8 workers so they need to add 18 - 8 = 10 new staff for the busy season.