Gasoline price 2

During the COVID-19 pandemic, Marilou's Gas Station gives a new gasoline price scheme to help our drivers. On their purchase, the first 4 liters cost Php 120.00, while the succeeding 1 1/2 liters would cost Php 10.00 more than the cost of a liter. If John bought 17 1/2 liters, how much should he pay?

Correct answer:

x =  660 Php

Step-by-step explanation:

$$\begin{gathered} V_1=4\text{l} \\ {c}_1=120.00/V_1=120.00/4=30\text{Php/l} \\ {c}_2=c_1+10=30+10=40\text{Php/l} \\ V=17\frac{1}{2}=17+\frac{1}{2}=\frac{17\cdot 2+1}{2}=\frac{34+1}{2}=\frac{35}{2}=17.5\text{l} \\ {V}_2=V-V_1=\frac{35}{2}-4=\frac{35}{2}-\frac{4\cdot 2}{2}=\frac{35}{2}-\frac{8}{2}=\frac{35-8}{2}=\frac{27}{2}=13.5\text{l} \\ x=V_1\cdot c_1+V_2\cdot c_2=4\cdot 30+\frac{27}{2}\cdot 40=660\text{Php} \end{gathered}$$

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