hi guys
please could you explain me this issue?
The population of a certain town increases by 50% every 50 years
If the population in 1950 was 810, in what year was the population 160?
thks
PERCENT TEST
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- indiantiger
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I think there should be a better method than this one do this question but anyways:
population in 1950 = 810
we need to find the year of population 160
Lets say the year was 19xx and population = 160
population increases by 1/2 of the previous population every year so
in 19xx+1, population was = 160+160/2 = 240
in 19xx+2, population was = 240+240/2 = 360
in 19xx+3, population was = 360+360/2 = 540
in 19xx+4, population was = 540+540/2 = 810
so 19xx+4 = 1950
19XX = 1946
Let me know if this makes sense
population in 1950 = 810
we need to find the year of population 160
Lets say the year was 19xx and population = 160
population increases by 1/2 of the previous population every year so
in 19xx+1, population was = 160+160/2 = 240
in 19xx+2, population was = 240+240/2 = 360
in 19xx+3, population was = 360+360/2 = 540
in 19xx+4, population was = 540+540/2 = 810
so 19xx+4 = 1950
19XX = 1946
Let me know if this makes sense
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the kaplan s explanation wasnt good at all below
" population in 1950 was 150% so 3/2 ??of the 1900 POPULATION
this means the 1900 population was 2/3? of 1950 population
similary the 1850 population was 2/3 of 1900 population, and so on.
"
why 2/3??
" population in 1950 was 150% so 3/2 ??of the 1900 POPULATION
this means the 1900 population was 2/3? of 1950 population
similary the 1850 population was 2/3 of 1900 population, and so on.
"
why 2/3??
- jeffedwards
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francoisph wrote:the kaplan s explanation wasnt good at all below
" population in 1950 was 150% so 3/2 ??of the 1900 POPULATION
this means the 1900 population was 2/3? of 1950 population
similary the 1850 population was 2/3 of 1900 population, and so on.
"
why 2/3??
Think of 2/3 this way.
Pretend we start with 10
Now let's increase that number by 50%
The new number would be 15 right.
Now, let's pretend we need to return back to 10.
If we times 15 by 2/3 we get 10
To reverse a 50% increase we have to decrease the new number by 33%, because the new number is larger.
Does that make sense?
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- jeffedwards
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indiantiger wrote:I think there should be a better method than this one do this question but anyways:
population in 1950 = 810
we need to find the year of population 160
Lets say the year was 19xx and population = 160
population increases by 1/2 of the previous population every year so
in 19xx+1, population was = 160+160/2 = 240
in 19xx+2, population was = 240+240/2 = 360
in 19xx+3, population was = 360+360/2 = 540
in 19xx+4, population was = 540+540/2 = 810
so 19xx+4 = 1950
19XX = 1946
Let me know if this makes sense
Oh just now read the post above. The population increase by 50% every 50 years. So it decreases by 33% going backwards
1950 - 810
1900 - 540
1850 - 360
1800 - 240
1750 - 160
So 1750 should be the answer
- indiantiger
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- jeffedwards
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you were mostly all on...i do that all the timeindiantiger wrote:@ jeffedwards,
Thanks for the correction, it has been a long day