Another SAT Question

Test Preparation
1

<p>Hi, </p>

<p>Once again I have another math question, but this time from the 2010 Practice</p>

<p>Can someone explain section 2 number 19? </p>

<p>On the day of a rainstorm, the depth of the water at a
certain location along the Winding River was recorded
hourly, and the results are indicated in the line graph
above. Each unit on the vertical axis represents 1 foot.
If the depth of the water decreased 10 percent from
3:00 P.M. to 4:00 P.M., what was the depth of the water
at 4:00 P.M.?
(A) 3 feet
(B) 15 feet
(C) 18 feet
(D) 20 feet
(E) 30 feet</p>

2

<p>Can’t do it without the “line graph above”</p>

3

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4

<p>C.</p>

<p>It was 20 ft and then it went to 18 ft</p>

5

<p>Test each of the choice by adding two feet (there are two lines) and seeing if 10% of the depth of the water at such time matches the difference between the two times.</p>

<p>It is C. 18 + 2 ft (1 ft = 1 line, there are two lines) = 20 ft. Test. What is 10% of 20? 2. Yayy</p>

6

<p>wait, how did you get 20 feet to begin with?</p>

7

<p>By inspection, the water depth decreased by 2 increments (2 feet) between 3PM and 4PM.</p>

<p>We are also told that the water depth reduced by 10% during this time.</p>

<p>Therefore:
10% = 2 feet
100% = 20 feet, where 100% represents the depth of water at 3PM</p>

<p>Hence, the water depth at 4PM is given by: 20 feet - 2 feet
=18 feet</p>