math

Test Preparation SAT Preparation
1

<p>alright I have some more math problems that I don't fully understand.</p>

<ol>
<li><p>three lines are drawn in a plane so that there are exactly three different interesection points. into how many nonoverlapping regions do these lines divide the plane?
a. three b. four c. five d. six e. seven</p></li>
<li><p>if s denotes the sum of integers from 1 to 30 inclusive and t denotes the sum of integers from 31 to 60 inclusive, what is the value of t-s?
a. 30 b. 31 c. 180 d. 450 e. 900</p></li>
</ol>

<p>all questions are from the collegeboard online course</p>

2

<ol>
<li><p>E
Draw a set of 3 lines that have three intersections. The lines should form a triangle, but should be infinitely long. Count the regions.</p></li>
<li><p>E
Subtract 1 from 31. 2 from 32. 3 from 33. See the pattern? So it’s 30*30 = 900.</p></li>
</ol>

3

<ol>
<li>Here’s a formula that can help on questions like #2 (although I prefer Subrosian’s method)</li>
</ol>

<p>(1st integer+last integer)/2 * number of terms = sum </p>

<p>so in this problem you would simply input
(1+30)/2 * 30 = 465</p>

<p>(31+60)/2* 30 = 1365</p>

<p>1365- 465 = 900 (E)</p>