Question

A truck covers a distance of 510 km in 34 litres of diesel. How much distance would it cover in 20 litres of diesel?

Answer 1

Let the required distance be x km. Then, we have:

Quantity of diesel (in litres)	34	20
Distance (in km)	510	x

Clearly, the less the quantity of diesel consumed, the less is the distance covered.
So, this is a case of direct proportion.
$$\begin{gathered} \mathrm{Now},\frac{34}{510}=\frac{20}{x} \\ \Rightarrow \frac{1}{15}=\frac{20}{x} \\ \Rightarrow x\times 1=20\times 15=300 \end{gathered}$$

Therefore, the required distance is 300 km.