# Ratio Questions

this question is stumping me which is a pain because it was found in a basic high school math book.

When a car is moving at 108 km/hr, it travels 18km on a litre of petrol. If petrol costs €1,62 a litre work out the cost of the petrol per minute when the car travels at 108 km/hr.

Any help for this question would be appreciated.

At 108 km/h we have a fuel consumption of 1/18 L/km, so the cost is $$\frac{1}{18} \frac{L}{km} \cdot 1.62~\frac{€}{L} = \frac{1.62}{18}~\frac{€}{km}$$ Then, since we are going at 108 km/h, that is $$\frac{1.62}{18}\frac{€}{km}\cdot108\frac{km}{h} = \frac{1.62\cdot 108}{18} \frac{€}{h} = \frac{1.62\cdot 108}{18\cdot 60} \frac{€}{min}= 0.162 \frac{€}{min}$$ Hope this helps.