A car covers $641\dfrac{1}{4}$km in $43\dfrac{1}{8}$ litres of fuel. How much distance can this car cover in 1 litre of fuel ?

Given:

Total distance = $641\dfrac{1}{4}\text{ km} = \dfrac{2565}{4}$ km

Total fuel = $43\dfrac{1}{8}\text{ litres} = \dfrac{345}{8}\text{ litres}$

Distance per litre = ?

Distance per litre = (Total distance) ÷ (Total fuel)

Substituting the values in above, we get:

Distance per litre = $\dfrac{2565}{4}\text{ km} ÷ \dfrac{345}{8}\text{ litres}$

$\begin{array}{ll} = \Big(\dfrac{2565}{4} \times \dfrac{8}{345}\Big)\text{ km} & [\text{Reciprocal of } \dfrac{345}{8} \text{ is } \dfrac{8}{345}] \\ = \Big(\dfrac{2565}{1} \times \dfrac{2}{345}\Big)\text{ km} & \text{[Simplifying 8 and 4 ⇒ Divide by 4]} \\ = \Big(\dfrac{171}{1} \times \dfrac{2}{23}\Big)\text{ km} & \text{[Simplifying 2565 and 345 ⇒ Divide by 15]} \\ = \dfrac{171 \times 2}{1 \times 23} \text{ km} \\ = \dfrac{342}{23} \text{ km} \\ = 14\dfrac{20}{23} \text{ km} \end{array}$

∴ The distance per litre of petrol = $14\dfrac{20}{23}$ km