Question

A car travels \[108\] km in \[12\] litres of petrol. In \[10\] litres of petrol it will cover a distance of
A. \[90\] km
B. \[518.4\] km
C. \[\dfrac{9}{{10}}\] km
D. \[\dfrac{{10}}{9}\] km

Answer 1

Hint: In this question, we are going to find the distance travelled by the car with one litre of petrol. Then we multiply this by 10 to get the distance that the car covers with 10 litres of petrol.

Complete step-by-step answer:
It is given that the car travels \[108\] km in \[12\] litres of petrol.
First, we will calculate how many kilometres the car travels with 1 litre.
For this, we are going to divide 108 by 12
Therefore, we have \[\dfrac{{108}}{{12}}\]
$ \Rightarrow \dfrac{{108}}{{12}} = 9$
Hence we can conclude that the car can travel 9 km with 1 litre of petrol.
Now, we are going to find the distance travelled by the car with \[10\] litres of petrol.
We already found that the car can travel 9 km with 1 litre of petrol. To find the distance covered by the car with 10 litres of petrol, we are going to multiply 9 by 10.
The distance travelled by the car with\[10\]litres of petrol \[ = 10 \times 9 = 90{\text{ km}}\].
Hence the car can travel 90 km with 10 litres of petrol.

Thus, the correct option is A. \[90{\text{ km}}\]

Note: The unitary method is 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.
The distance travelled by the car in 12 litres is greater than the distance travelled by the car in 10 litres since, 12 litres of petrol is more than 10 litres of petrol. Hence we clearly say that the distance covered by the car with 10 litres of petrol is lesser than the distance covered by the car with 12 litres of petrol. Therefore 90 < 108. In this way, we can check our answer.