AMC8 2024

AMC8 2024 · Q10

AMC8 2024 · Q10. It mainly tests Rounding & estimation, Arithmetic sequences basics.

In January $1980$ the Mauna Loa Observatory recorded carbon dioxide $(CO2)$ levels of $338$ ppm (parts per million). Over the years the average $CO2$ reading has increased by about $1.515$ ppm each year. What is the expected $CO2$ level in ppm in January $2030$? Round your answer to the nearest integer.

1980 年 1 月，Mauna Loa 观测站记录的二氧化碳 $(CO_2)$ 水平为 $338$ ppm（百万分之一）。多年来，平均 $CO_2$ 阅读值每年增加约 $1.515$ ppm。2030 年 1 月的预期 $CO_2$ 水平是多少 ppm？四舍五入到最近的整数。

(A) \ 399 \ 399

(B) \ 414 \ 414

(D) \ 444 \ 444

(E) \ 459 \ 459

Answer

Correct choice: (B)

正确答案：（B）

Solution

This is a time period of $2030 - 1980 = 50$ years, so we can expect the ppm to increase by $50*1.515=75.75\approx 76$ ppm. Since we started with $338$ ppm, we have $76+338=\boxed{\textbf{(B) 414}}$.

时间跨度为 $2030 - 1980 = 50$ 年，因此预期增加 $50 \times 1.515 = 75.75 \approx 76$ ppm。起始 $338$ ppm，故 $76 + 338 = \boxed{\textbf{(B) 414}}$。

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