Jared's room painting

Jared wants to paint his room. It is 12 feet by 15 feet and has walls 9 feet high. Two windows measure 6 feet by 5 feet each, and two doors measure 30 inches by 6 feet each. If a gallon of paint covers approximately 350 square feet, how many gallons will it take to paint the walls two layers of color?

Correct answer:

x =  3.2914 gal

Step-by-step explanation:

$$\begin{gathered} a=12\text{ft} \\ b=15\text{ft} \\ c=9\text{ft} \\ {w}_1=6\text{ft} \\ {w}_2=5\text{ft} \\ {d}_1=30\text{inch}\to \text{ft}=30:12\text{ft}=2.5\text{ft} \\ {d}_2=6\text{ft} \\ h=350{\text{ft}}^2\text{/gal} \\ {S}_1=a\cdot b+2\cdot (a+b)\cdot c=12\cdot 15+2\cdot (12+15)\cdot 9=666{\text{ft}}^2 \\ W=w_1\cdot w_2=6\cdot 5=30{\text{ft}}^2 \\ D=d_1\cdot d_2=2.5\cdot 6=15{\text{ft}}^2 \\ S=S_1-2\cdot W-2\cdot D=666-2\cdot 30-2\cdot 15=576{\text{ft}}^2 \\ x=2\cdot S/h=2\cdot 576/350=3.2914\text{gal} \end{gathered}$$

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