I29-162

Question

https://gmatclub.com/gmat-focus-tests/resources/import/img/I29-162.png 
 
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.

Country X’s total population had to increase by the greatest percentage from the previous century to the  GRAPH_1_PLACEHOLDER  Century, when the total population had to increase by  GRAPH_2_PLACEHOLDER .

Bunuel · Answer

Official Solution:

To determine how much the total population  had to  increase from one century to the next, focus on the region whose share decreased the most. Since every region’s actual population increased, the smaller percentage in the next century still had to represent more people than the larger percentage in the previous century. For example, if a region’s share fell from 50% to 40%, then 40% of the new total had to be greater than 50% of the previous total.
 
•  17th to 18th Century:  Desert fell from 50% to 40%. Suppose the total population in the 17th Century was 100, so Desert had 50 people. In the 18th Century, Desert’s population was more than 50 and represented 40% of the new total. For 40% of the new total to exceed 50, the new total must have been more than 125, implying an increase of more than 25%.
 
•  18th to 19th Century:  Desert fell from 40% to 25%. If the 18th-Century total was 100, then Desert had 40 people. In the 19th Century, 25% of the new total had to exceed 40, so the new total had to be more than 160, which means an increase of more than 60%.
 
•  19th to 20th Century:  Desert fell from 25% to 10%. If the 19th-Century total was 100, then Desert had 25 people. In the 20th Century, 10% of the new total had to exceed 25, so the new total had to be more than 250. Thus, the new total had to be more than 2.5 times the previous total, which corresponds to an increase of more than 150%.
 
Thus, Country X’s total population had to increase by the greatest percentage from the 19th Century to the  20th  Century, when it had to increase by  more than 150% .

Correct answer:

Dropdown 1:  "20th"

Dropdown 2:  "more than 150%"

rayansinha · Answer