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Bunuel
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Bunuel
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fugaquasi
Hi Bunuel , Im a confused why the second part is more than 150%, actually im confused how can we even tell anything about the total population from a graph of relative populations that are all increasing and always add upto 100 ?

The OE will be published soon. Let’s wait to see if anyone else shares solutions in the meantime.
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The intuition is as follows: Suppose there are 100 people living in the 19th century. For example, 25 of them lived in the desert. In the 20th century, this group increased by an amount x. Although their total number grew, their percentage share fell to 10%. Thus, 25 + x now equals 10% of the total population. Therefore, the total population is 10 times (25 + x), which is greater than 250, representing an increase of more than 150%.
Hope this makes sense.

fugaquasi
Hi Bunuel , Im a confused why the second part is more than 150%, actually im confused how can we even tell anything about the total population from a graph of relative populations that are all increasing and always add upto 100 ?
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Bunuel


The chart shows the percentage of the total population of Country X, measured at the end of each century, living in each of its four regions (Lowland, Highland, Coastal, and Desert). In each century, the population of every region increased compared with the prior century.

From each drop-down menu, select the option that creates the most accurate statement based on the information given.

The largest percentage increase in the total population from one century to the next occurred in the Century, when the total population increased by .

Attachment:
GMAT-Club-Forum-x8kdoala.png
The crux of this question lies in the statement : “ In each century, the population of every region increased compared with the prior century “.


let’s take the 17th century population as 100. So, the lowland population: 10, Highland : 35, Coastal : 5, Desert: 50.

Look at the yellow bar ( DESERT) : In 17th century, it’s 50.

18th Century, let the total population be Y. 40%(Y) > 50. We get, Y > 125.

so, let’s take the population of 18th Century as 200.

Lowland : 30, Highland : 66, Coastal : 24 and Desert: 80.

Look at the yellow bar for 19th century, which is 25%. Let the population of 19th century be Z.

25% Z > 80. Then, Z > 320.

So, let the population of Z be 360.

Lowland : 65, Highland : 115, Coastal : 90 and Desert: 90.

Look at the yellow bar for 20th Century, which is 10%. Let the population of 20th century be P.

10% P > 90.

Thus, P has to be > 900.

Lets us take P =1000.

The individual values for 20th century are : Lowland (200), Highland (200), Coastal (450), Desert (100).

So, the POPULATION INCREASE is highest from 19th century to 20th century.

360 ————————> 1000 ( increase of 640)

640/360 = 177.77% ( MORE THAN 150% ).
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Thank you so much for explaining this
Dereno

The crux of this question lies in the statement : “ In each century, the population of every region increased compared with the prior century “.


let’s take the 17th century population as 100. So, the lowland population: 10, Highland : 35, Coastal : 5, Desert: 50.

Look at the yellow bar ( DESERT) : In 17th century, it’s 50.

18th Century, let the total population be Y. 40%(Y) > 50. We get, Y > 125.

so, let’s take the population of 18th Century as 200.

Lowland : 30, Highland : 66, Coastal : 24 and Desert: 80.

Look at the yellow bar for 19th century, which is 25%. Let the population of 19th century be Z.

25% Z > 80. Then, Z > 320.

So, let the population of Z be 360.

Lowland : 65, Highland : 115, Coastal : 90 and Desert: 90.

Look at the yellow bar for 20th Century, which is 10%. Let the population of 20th century be P.

10% P > 90.

Thus, P has to be > 900.

Lets us take P =1000.

The individual values for 20th century are : Lowland (200), Highland (200), Coastal (450), Desert (100).

So, the POPULATION INCREASE is highest from 19th century to 20th century.

360 ————————> 1000 ( increase of 640)

640/360 = 177.77% ( MORE THAN 150% ).
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fugaquasi LucaBas34

The largest percentage increase in the total population from one century to the next occurred in the Century, when the total population increased by .

Largest population increase: Here we are bothered only about bars which are going up between one century to other, Why because, the decrease which are happening in another regions are compensated by the increase.

from 17th to 18th century: Net increase is 5+7=12 (Lowland 5% and Coastal 7%)
18th to 19th: Net increase is 16 (Lowland 3% Coastal 13%)
19th to 20th: Net increase is 22 (Lowland 2 and Coastal 20)
Thus highest increase is in 20th century

Now we can take the highest increase which happened, that is 19th century coastal from 25% to 45%
Let the overall population in 19th be x and 20th be y
We have 25% of X=45% of Y
Or X/4=9Y/20
X=9Y/5
X is approximately 1.8Y, which is more than 160%
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