Case Interview Tools - Replacement Concept (1/3) | PrepLounge 

I'm not sure whether to be more amazed at the concept, or the fact that you can write backwards.

Good concept. However it's only applicable to the following situation: 1.When you talk about the whole population, rather than a particular group .(e.g doctors), then you can use the population data of one country 2.The goods are regular replaceable household goods(e.g light bulbs, car,fridge) For other types of goods, such as gift chocolate, it would be very difficult to generate.

The replacement concept is a powerful tool for cracking cases.

Wow, I wouldn't have even known were to begin.

what impresses me most is that he can write mirrored :D

This is Little's Law... not Replacement Concept

maybe the video was just inverted on the x axis

Is his conclusion right? I think that when you correct the value (100M) to account for the population growth rate of 1%, the number of babies that need to be born is 101M, not 170M... am I mistaken?

blew my mind :D i feel so stupid now

you can actually solve this without the replacement concept; try using the average TFR of developed countries (and developing ones) * total population of women in the respective segments.

I don't quite get this. How is Total population / Life expectancy = number of people died?