A water-quality survey measured the nitrate concentration in a river

Question

https://gmatclub.com/forum/download/file.php?id=89808 A water-quality survey measured the nitrate concentration in a river at various distances downstream from its source. The horizontal axis shows distance from the source, in kilometers, and the vertical axis shows nitrate concentration, in milligrams per liter. The shaded regions indicate sections of the river bordered by intensive agricultural land. Select from each drop-down menu the option that completes the statement most accurately based on the information provided. The local peaks in nitrate concentration occur nearest the GRAPH_1_PLACEHOLDER of the shaded agricultural sections. Immediately downstream of the agricultural section ending at 20 km, nitrate concentration GRAPH_2_PLACEHOLDER than it did immediately downstream of the section ending at 65 km. GMAT-Club-Forum-ei6ytetl.png

Bunuel · Accepted Answer

https://gmatclub.com/forum/download/file.php?id=89808

A water-quality survey measured the nitrate concentration in a river at various distances downstream from its source. The horizontal axis shows distance from the source, in kilometers, and the vertical axis shows nitrate concentration, in milligrams per liter. The shaded regions indicate sections of the river bordered by intensive agricultural land.

Select from each drop-down menu the option that completes the statement most accurately based on the information provided.

The local peaks in nitrate concentration occur nearest the  GRAPH_1_PLACEHOLDER  of the shaded agricultural sections.

Immediately downstream of the agricultural section ending at 20 km, nitrate concentration  GRAPH_2_PLACEHOLDER  than it did immediately downstream of the section ending at 65 km.

Official Solution:

Drop-down 1:

Look at where the high points of the curve occur relative to the shaded sections.

The nitrate concentration reaches local peaks at approximately 20, 40, 65, and 85 km. Each of these points lies at or very near the end of a shaded agricultural section.

Therefore, the correct selection is  end .

Drop-down 2:

Compare how the graph behaves immediately after the two shaded sections.

After the section ending at 20 km, nitrate concentration falls from about 6.4 mg/L at 20 km to about 4.2 mg/L at 25 km, a decrease of about 2.2 mg/L.

After the section ending at 65 km, it falls only from about 7.1 mg/L at 65 km to about 6.8 mg/L at 70 km, a decrease of about 0.3 mg/L.

Thus, immediately after the section ending at 20 km, the concentration decreased much more sharply.

Therefore, the correct selection is  decreased much more sharply .

Correct answer:

Drop-down 1: "end"
Drop-down 2: "decreased much more sharply"

officiisnobis · Answer

1. End 
2. Decreased much more sharply

GridLock · Answer

1 is focusing on the section of the shaded region (beginning, middle, end). The peaks in all shaded region happen towards the end of the regions. 
Therefore end.

2 is focusing on the section immediately after the shaded region. Concentration always decreased after the shaded region. But it decreased much more sharply following the first shaded region compared to the third shaded region. 
Therefore, decreased much more sharply.

LogicDriven · Answer

First blank: ==> end
The nitrate levels peak right near the end of each agricultural area.

Second blank ==> decreased much more sharply
After the first agricultural section (at 20 km), the nitrate levels plunge down fast and steep. After the 65 km section, the drop is much slower and gentler.

Shyam97 · Answer

1. End ----- highest nitrate concentration in end boundary of shaded section
2. Decreased much more sharply

A water-quality survey measured the nitrate concentration in a river

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Graphs and Tables (G&T) Questions

A water-quality survey measured the nitrate concentration in a river

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards