SAT Question of the Day for June 2nd

Test Preparation SAT Preparation
1

<p>Today’s Question
Monday, June 2</p>

<p>Read the following SAT test question, then click on a button to select your answer.</p>

<p>The stopping distance of a car is the number of feet that the car travels after the driver starts applying the brakes. The stopping distance of a certain car is directly proportional to the square of the speed of the car, in miles per hour, at the time the brakes are first applied. If the car’s stopping distance for an initial speed of 20 miles per hour is 17 feet, what is its stopping distance for an initial speed of 40 miles per hour?</p>

<li>34 feet</li>
<li>51 feet</li>
<li>60 feet</li>
<li>68 feet</li>
<li>85 feet</li>
</ol>

<p>How is that of “medium” difficulty? I didn’t understand the explanation CB has for this one. Can someone explain it to me in a more lucid way? Thank you.</p>

2

<p>17/20^2 = x/40^2<br>
x=(17 * 1600)/400
x=68</p>

<p>that should be right</p>

3

<p>LOL use physics to solve it. Easy</p>

4

<p>It’s medium difficulty because you might not understand what it’s asking. However, once you do know, it’s just a matter of plugging and chugging. The above explanation is correct. It doesn’t really require any out of the box thinking; once you know how to do one, you know how to do them all.</p>

5

<p>answer should be 34.
they are proportional.
20miles to 40 miles
17ft to what ft</p>

<p>20/17=40/x
x is 34.</p>

<p>edit: my answers wrong, omg wats going on/?</p>

<p>2nd edit: omg, stupid mistake, misread the problem…i didnt see the “square of the speed”, stupid careless mistakes, this is why i cant get a high score in math,-.-</p>

6

<p>the key is “directly proportional to the square of the speed of the car.”</p>

<p>what you did, would work if the question said ‘directly proportional to the speed of the car.’</p>

7

<p>so,basically, if u know how ratio works, proportionality stuff, u would be okay.
remember, apple to apple, orange to orange. miles to miles, ft to ft, doesn’t matter miles the numerator or denominator.</p>

8

<p>Everytime you see directly proportional to something, just remember:
y=kx or in this case, y=kx^2.</p>

<p>Applying the problem:
17=k(20^2)
k=.0425 (17/400)</p>

<p>y=(17/400)(40^2)
=(17/400)(1600) = 17 * 4 = 68 – this is the answer.</p>

9

<p>yeahh i thought it was really really, and i really would have gotten the right answer if i didn’t forget that it was a squared term. so sad…i totally knew how to do it and everything >.<</p>

10

<p>It took me a good two minutes to figure out (which, as everyone knows, is a lot for an SAT problem), and you’re right, it’s really more of a medium/hard question, maybe #17 in a section of 20. The math is easy, but then again all of the math is easy on the SAT; it’s the applying of the math that’s difficult, and it can tricky to set up the correct equation.</p>

11

<p>Hey, WantIvy, what is the formula of indirect variability questions? I always remember the direct one, but not the other.</p>

12

<p>direct: y = kx
indirect: y = k/x</p>

<p>“k” is the constant.</p>

13

<p>Another way to put that is
Direct: x1/x2 = y1/y2
Indirect: x1<em>x2 = y1</em>y2</p>