Question

A journey of 500km is covered by a car using 20 litres of petrol. How much petrol will be used for a journey of 750 km? what will be the distance that the car can travel with 27 litres of petrol?

Answer 1

Hint:-We are solving this by the unitary method. It’s a technique for solving a problem by first finding the value of a single unit, and then finding the necessary value by multiplying the single unit value. In essence, This method is used to find the value of a unit from the value of a multiple, and hence the value of a multiple.

Complete step-by-step answer:
According to question,
500 km covered by a car of 20 its petrol.
So, 500 km required 20 its petrol
$\therefore $ 1 km required $\dfrac{{20}}{{500}}$its petrol
$\therefore $ 750 km required $\dfrac{{20 \times 750}}{{500}}$ for its petrol.
          $ = 30$ litres petrol.
So, 750 km required 30 litres of petrol.
And
With 20 it of petrol car can travel 500 km
$\therefore $ with 1 it of petrol Car can travel $\dfrac{{500}}{{20}}km\;\;\;\;\; = 25km$
$\therefore $with 27 it of petrol car can travel $\left( {25 \times 27} \right) = 675km$
So, with 27 litres of petrol a car can travel 675 kilometres.


Note: We have to care about where we have to multiply or where we have to divide, line for this problem if 20 its is required for 500 km then it is obvious that for 1 km we have to divide because for 1 km the amount of petrol required is a lever that the amount of petrol required for 500 km. take care of this thing where we have to multiply and where we have to divide.