easy math question

Test Preparation SAT Preparation
1

<p>help me get it</p>

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<a href="http://tapatalk.com/mu/ae373148-0d85-e316.jpg%5B/IMG%5D"&gt;http://tapatalk.com/mu/ae373148-0d85-e316.jpg

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2

<p>I’ll take the plunge…“C”. I tried all the variables and that was the one. I love math problems after 11pm… Makes me keep up with my kids.</p>

3

<p>(t-k)(t+k) < 6
Since t-k > 0 (given t>k) and t+k>4
t+k must =5; then t-k=1.
Therefore t=3.</p>

4

<p>I would use the strategy of “starting with choice (C).” </p>

<p>If we “guess” that the answer is (C), then t=3. </p>

<p>Since t > k, and k is a positive integer, k must be 1 or 2. </p>

<p>From the first inequality, we have 9 - k^2 < 6. So k must be 2 (9 - 4 = 5 < 6, but 9 - 1 = 8 > 6). </p>

<p>We now check to see if these values for t and k work in the second inequality:</p>

<p>t + k = 3 + 2 = 5 > 4. </p>

<p>It works, so the answer is choice (C).</p>

5

<p>That’s a medium question by the way (L3), not easy. CC excepted of course.</p>

6

<p><a href=“t-k”>quote</a>(t+k) < 6
Since t-k > 0 (given t>k) and t+k>4
t+k must =5; then t-k=1.
Therefore t=3.

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<p>As this shows, there is no need to play with guesses and plug ins. It only takes one simple operation (and remembering a must-know rule)</p>

<p>As soon as t^2 -k^2 < 6 is written as
(t-k)(t+k) < 6, one can immediately conclude that
t-k has to be 1, and t can only be 3 (and k=2)</p>