Interview Question : Finding Number Of Cars in City

Finding Total Number Of Cars ..... interview

Interview was going on .... then one interviewer asked :

One Interviewer Asked: Assume that the population of Delhi is 2 crores (20 million)

How many number of car are there in Delhi City?

...........................................................

( Candidate) she get it quickly that this is a type of guesstimate. 

There is no correct/incorrect answer in this case and the interviewer usually wants to see thought process in such question.

Candidate Replied : 

As the population of Delhi is 2 crores (20 million)

Let the average family size in Delhi be 4 So the number of households can be estimated to be 50 lakhs (20/4 million)

Now, let us assume that only 50 - 60% of the population can afford a car.

 For simplicity, assume that 50% of the families owns one or more cars.
So 25 lakh households own 1 or more cars

Let us assume that of these, 75% own only 1 car , 20% own 2 cars and 5% own 3 cars (assuming no household has more than 3 cars)


So households with 1 car = 18.75 lakh(1.875 million) 2 car = 5 lakh (500,000) 3 car = 1.25 lakh ( 125,000)


So total number of cars in delhi can be estimated as 18.75 + 5*2 + 1.25*3 = 32.5 lakh which can be rounded off to 32 lakh (3.2 million)


So we can estimate that the number of cars in Delhi to be 32 lakh (3.2 million).

------------------------------------------------------------------------------------------------------------

Interviewer gave her good scores for her thought process