1998 AMC 8 Problem 15

Below is the professionally curated solution for Problem 15 of the 1998 AMC 8, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1998 AMC 8 solutions, or check the answer key.

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Concepts:geometric sequenceestimation

Difficulty rating: 960

15.

Problems 15,16,15, 16, and 1717 all refer to the following:

Don’t Crowd The Isles

In the very center of the Irenic Sea lie the beautiful Nisos Isles. In 19981998 the number of people on these islands is only 200,200, but the population triples every 2525 years. Queen Irene has decreed that there must be at least 1.51.5 square miles for every person living in the Isles. The total area of the Nisos Isles is 2490024900 square miles.

Estimate the population of Nisos in the year 2050.2050.

600600

800800

10001000

20002000

30003000

Solution:

The population in 20482048, which is 5050 years after 19981998, is 32200=18003^2\cdot200=1800.

Since 20482048 is close to 20502050, the population in 20502050 is approximately 18001800, and the closest choice is 20002000.

Thus, the correct answer is D .

Problem 15 in Other Years

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