Calculation - Number of People Who are Sick

Nutripremium
New answer on Feb 27, 2020
5 Answers
886 Views
Anonymous A asked on Feb 22, 2020

Hi

Could you pls explain to me why we have to multiply 5/75 with 2/100? I don't get the logic behind it... How come we can use this multiplication to determine how many people are ill?

Looking forward to hearing from you!

Cheers

(edited)

Overview of answers

Upvotes
  • Upvotes
  • Date ascending
  • Date descending
Best answer
Luca
Expert
Content Creator
replied on Feb 27, 2020
BCG |NASA |20+ interviews with 100% success rate| 120+ students coached |GMAT expert 780/800 score

Hello,

2% is the population having a cancer in his life. The next step is: if one has a cancer in his life, what is the probability that he has a cancer in this moment? This probability is 5/75, the percentage of the years of your life spent having a cancer if you are sick.

Hope it helps,
Luca

Was this answer helpful?
Clara
Expert
Content Creator
replied on Feb 24, 2020
McKinsey | Awarded professor at Master in Management @ IE | MBA at MIT |+180 students coached | Integrated FIT Guide aut

Hello!

To your prompt > Why do I have to multiply 5/75 with 2/100?

  • 75 > Average age of the female chinese population -target group-.
  • 5 > Asuming that cancer leasts of 5 years (assumption)
  • 2/100 > 2% of the population will suffer from cancer at some point.

Hope it helps!

Cheers,

Clara

Was this answer helpful?
Vlad
Expert
Content Creator
updated an answer on Feb 24, 2020
McKinsey / Accenture Alum / Got all BIG3 offers / Harvard Business School

Hi,

Pls study Age Groups - that's one of the most commonly used tools in market sizing questions.

If 75 years is the av life expectancy and we assume for simplicity that the population is evenly distributed, we have 1/75 people of each age

Best

(edited)

Was this answer helpful?
Anonymous A on Feb 26, 2020

Hi Vlad! Thanks for this recommendation! Indeed, I started with this difficult case... but at least now I know that I have to know age groups.

Antonello
Expert
Content Creator
replied on Feb 23, 2020
McKinsey | MBA professor for consulting interviews

- 2% of the people get a cancer once in life;
- If you consider the population evenly distributed with ages you have for each age group 1/75 of the population;
- If cancer lasts on average 5 years you should multiply the population per 5* 2% * 1/75.

Best,
Antonello

Was this answer helpful?
Ian
Expert
Content Creator
replied on Feb 23, 2020
BCG | 100% personal interview success rate (8/8) and 95% candidate success rate | Personalized interview prep

75 = life expectancy of a chinese woman

5 = average duration of having cancer

2/100 = 2% of population having cancer at some point in their lives.

So, you are basically taking 5/75 and multiplying it by 2%

What we are saying is that 2% of the population will have cancer at some point. And, they will have it for 5 years out of their 75. So, at any given point in time, .13% will be sick (the 2% of people for 5/75 of the time)

Was this answer helpful?
Luca gave the best answer

Luca

Content Creator
BCG |NASA |20+ interviews with 100% success rate| 120+ students coached |GMAT expert 780/800 score
56
Meetings
2,683
Q&A Upvotes
29
Awards
19 Reviews