<p>Let's post some things we should all remember for tomorrow's SAT Math section. </p>
<p>By the way, can somebody please clarify permutations/combinations? I'm having a hard time differentiating between the two..</p>
<p>I have never seen a Permutation problem on any practice test I’ve taken. Highly doubt it’ll be on it.</p>
<p>The way I remember permutations v. combinations:</p>
<p>combinations: order doesn’t matter. The trick I use is that Nobody cares about cordaroy.
Example: If there are 10 people, how many ways can they fill up two parking spaces. These people are all the same, so just type into ur calc 10 C 2</p>
<p>permutations: order does matter. This is the one you use when the things ur doing are different. Example: There are 10 people. They are running for president, vice president, secretary. How many ways can they do this? This is 10 P 3
Prez, Vice prez, secretary are all different so order does matteer so u would use permutation</p>
<p>Where can you find the C and P in your calculator. I have a ti 84 plus silver.</p>
<p>Don’t forget to look at the <,> signs
make sure you read every question thoroughly
that’s about all I have.</p>
<p>math>PRB(use the left/right arrows)>nPr/nCr</p>
<p>make sure to input a number before and after the symbol</p>
<p>10C2 (10 people filling up 2 spots, where order doesnt matter) looks like 10 nCr 2
you should get 45 for 10C2</p>
<p>I found nPr but not nPc…Instead there was nKr. I’m guessing these are the same.</p>
<p>I never understood how to use the calculator combination/permutation stuff, but my way is equally as effective and makes more sense conceptually (in my opinion).
Whenever it’s combination, find the permutation first and divide that permutation by n. In the basic sense, n is the number of “slots” available.
For example,
If there are 10 people, how many ways can they fill up two parking spaces?
10 * 9
90 permutations
n = 2 (the 10 as one slot, and the 9 as another).
90/2 = 45 combinations.</p>