# Calculation - Number of People Who are Sick

Nutripremium
New answer on Feb 27, 2020
5 Answers
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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)

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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

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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)

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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.

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

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- 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

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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)

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Luca gave the best answer
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