Estimation questions come in various forms, but in my experience, they can be categorized into two main groups.
These involve questions related to the magnitude of certain aspects, such as the storage cost of Instagram every year. The general method for approaching these questions is to calculate size (X) as the product of the number of units (Y) and the price per unit (Z).
In the case of a question concerning the storage cost of Instagram per year, the approach would be: Size (X) = number of users (Y) * Storage usage in gigabytes per year (Z) * cost per gigabyte (C).
These types of questions often take the form of 'the number of X within Y,' such as determining the number of restaurants in a city.
The typical approach is to employ the demand-supply method, meaning volume (X) = demand units (Y) / supply units (Z).
For instance, when estimating the number of 10-dollar meals served in NYC restaurants, one could adopt the following approach: Number of meals consumed at restaurants in a day (Y) that cost $10 a dish/number of meals one restaurant can serve in a day that cost $10 (Z)
Alternatively, you can tackle this question by calculating the area of the city and estimating the number of restaurants that can be accommodated within that area. While the demand-supply method is the primary approach, using the area method can serve as a means to cross-verify your answer.
