The area of a rectangle is width (w) x height (h). In this problem we know that the rectangle is twice as long as it is wide so h = 2w. The perimeter of a rectangle is 2w + 2h and we know that the perimeter of this rectangle is 12 meters so the equation becomes: 2w + 2h = 12.

Putting these two equations together and solving for width (w):

2w + 2h = 12
w + h = \( \frac{12}{2} \)
w + h = 6
w = 6 - h

From the question we know that h = 2w so substituting 2w for h gives us:

w = 6 - 2w
3w = 6
w = \( \frac{6}{3} \)
w = 2

Since h = 2w that makes h = (2 x 2) = 4 and the area = h x w = 2 x 4 = 8 m²

A ratio of 3:1 means that there are 3 home fans for every one visiting fan. So, of every 4 fans, 3 are home fans and \( \frac{3}{4} \) of every fan in the stadium is a home fan:

48,000 fans x \( \frac{3}{4} \) = \( \frac{144000}{4} \) = 36,000 fans.

To find the average of these 4 numbers add them together then divide by 4:

\( \frac{9 + 7 + 9 + 7}{4} \) = \( \frac{32}{4} \) = 8

53% of the water consumption is industrial use and 22% is personal use so (53% - 22%) = 31% more water is used for industrial purposes. 35,000 gallons are consumed daily so industry consumes \( \frac{31}{100} \) x 35,000 gallons = 10,850 gallons.

The first few multiples of 4 are [4, 8, 12, 16, 20, 24, 28, 32, 36, 40] and the first few multiples of 10 are [10, 20, 30, 40, 50, 60, 70, 80, 90]. The first few multiples they share are [20, 40, 60, 80] making 20 the smallest multiple 4 and 10 have in common.