Question

A car runs 16 km using 1 litre petrol. How much distance will it cover using $ 2\dfrac{3}{4} $ litres of petrol?

Answer 1

Hint: The distance covered by the car using 1 litre petrol is given, the distance it covers in $ \dfrac{{11}}{4}l $ can be calculated using a unitary method.
Example of unitary method:
If a quantity A has value x, then another quantity in terms of B can be written as:
A = x
B = $ \dfrac{x}{A} \times B $

Complete step-by-step answer:
Converting $ 2\dfrac{3}{4} $ litres from mixed fraction to improper fraction:

 $ \Rightarrow \left( {\dfrac{{4 \times 2 + 3}}{4}} \right)l = \dfrac{{11}}{4}l $
Now, it is given that the car runs 16 km using 1 litre petrol. The distance it covers in $ \dfrac{{11}}{4}l $ can be calculated using unitary method:
\[1l\]= 16 km
 $ \Rightarrow \dfrac{{11}}{4}l = \left( {\dfrac{{16}}{1} \times \dfrac{{11}}{4}} \right)km $
 $ \Rightarrow \dfrac{{11}}{4}l $ = 44 km.
Therefore, the distance a car will cover using $ 2\dfrac{3}{4} $ litres of petrol is 44 km.

Note: If we have any given quantity as a mixed fraction, we always have to convert it into an improper fraction and this can be done as follows:
 $ a\dfrac{b}{c} = \dfrac{{a \times c + b}}{c} $
Property of an improper fraction is that its numerator is greater than or equal to its denominator, this is also a reason why these are known as improper.
Remember:
While performing the unitary method, the quantity whose value is to be found or calculated is always kept at the right hand side (RHS) of the equation whereas the quantity whose value is known is to be kept on the left hand side (LHS) of the equation.