Gasoline fuel

You just drove your car 300 miles and used 40 gallons of gas. Your car's tank holds 12 1/2 gallons of gas, and if the gas you buy is $2.50 per gallon, what would you pay to fill one-half of your tank?

Correct answer:

x =  15 ⁵⁄₈ = 125/8 USD

Step-by-step explanation:

$$\begin{gathered} V_1=12\frac{1}{2}=12+\frac{1}{2}=\frac{12\cdot 2+1}{2}=\frac{24+1}{2}=\frac{25}{2}=12.5\text{gal} \\ {V}_2=V_1/2=\frac{25}{2}/2=\frac{25}{2\cdot 2}=\frac{25}{4}=6.25\text{gal} \\ x=2.5\cdot V_2=2.5\cdot \frac{25}{4}=\frac{125}{8}\text{USD}=15\frac{5}{8}\text{USD}=15.625\text{USD} \end{gathered}$$

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