Two of the walls have area $\displaystyle 20 \cdot 8 = 160\;\textrm{in}^{2}$; two have area $\displaystyle 18 \cdot 8 = 144\;\textrm{in}^{2}$; the ceiling has area $\displaystyle 20 \cdot 18 = 360\;\textrm{in}^{2}$. 

Therefore, the total area Steve wants to cover is 

$\displaystyle A = 160 + 160 + 144 + 144 + 360 =968 \; \textrm{in}^{2}$

Divide 968 by 360 to get the number of gallons Steve needs to paint his bedroom:

$\displaystyle 968 \div 360 \approx 2.7$

Since $\displaystyle 2 \frac{1}{2} < 2.7 < 2\frac{3}{4}$, Steve needs to purchase either two gallon cans and three quart cans, or three gallon cans. 

The first option will cost him $\displaystyle 36 \cdot2 + 13 \cdot3 = \$111$; the second option will cost him $\displaystyle 36 \cdot3 = \$108$. The latter is the more economical option.

The area of a rectangle is the product of its length and its height:

$\displaystyle 12.6 \cdot6.4 = 80.64$

The rectangle has a perimeter of 80.64 square centimeters.

The area of a rectangle is the product of its length and its width:

$\displaystyle 7 \frac{1}{2} \cdot 5 \frac{3}{5}$

$\displaystyle =\frac{7 \cdot 2 + 1}{2} \cdot \frac{5\cdot 5 + 3}{5}$

$\displaystyle =\frac{15}{2} \cdot \frac{28}{5} =\frac{3}{1} \cdot \frac{14}{1} = 42$

The area of the rectangle is 42 square inches.

100 centimeters make one meter, so convert each of the dimensions of the box by multiplying by 100.

$\displaystyle 0.9 \times 100 = 90$ centimeters

$\displaystyle 0.6 \times 100 = 60$ centimeters

Use the surface area formula, substituting $\displaystyle L = 90, W = H = 60$:

$\displaystyle A = 2LH + 2LW + 2HW$

$\displaystyle A = 2 \cdot 90 \cdot 60 + 2\cdot 90 \cdot 60 + 2 \cdot 60 \cdot 60$

$\displaystyle A = 10,800 + 10,800 + 7,200 = 28,800$ square centimeters

To make this easier, we will assume that the rectangle has length 5 and the square has sidelength 3. Then the area of the entire figure is 

$\displaystyle (3 + 5) \times 3 = 24$,

and the area of the square is 

$\displaystyle 3 \times 3 = 9$

The square, therefore, takes up

$\displaystyle \frac{9}{24} \times 100 = \frac{900}{24} = 37.5 \%$

of the entire figure.

The area of the rectangle is $\displaystyle 50\: in^{2}$. In order to find the area of a rectangle, multiply the length (5 inches) by the width (10 inches). The answer is in units² because the area, by definition, is the number of square units that cover the inside of a figure.

The pool can be seen as a rectangular prism with dimensions 24 meters by 15 meters by 2 meters; its volume is the product of these dimensions, or

$\displaystyle 24 \times 15 \times 2 = 720$ cubic meters.

The large rectangle has length 80 and width 40, and, consequently, area

$\displaystyle 80 \times 40 = 3,200$.

The white region is a rectangle with length 30 and width 20, and, consequently, area 

$\displaystyle 30 \times 20 = 600$.

The white region is 

$\displaystyle \frac{600}{3,200} \times 100 = 18 \frac{3}{4} \%$

of the large rectangle.

The formula for the area, $\displaystyle A$, of a rectangle when we are given its length, $\displaystyle L$, and width, $\displaystyle W$, is $\displaystyle A = L * W$.

To calculate this area, just multiply the two terms.

$\displaystyle A = 14\ cm * 12\ cm = 168\; cm^{2}$

Figure A has area $\displaystyle 10 \times 14 = 140$ square inches.

Figure B has area $\displaystyle 12 \times 12 = 144$ square inches, 1 foot being equal to 12 inches.

Figure C has area $\displaystyle \frac{1}{2} \times 16 \times 20 = 160$ square inches.

The figures, arranged from least area to greatest, are A, B, C.