<p>So uhm, SAT usually asks you combination-type problems. So I was wondering since Permutation = order important and combination = order don't matter,</p>
<p>Does permutation mean everything is multiplied or does combination mean multiply everything?</p>
<p>[YouTube</a> - Combination Permutation SAT Math Problem/Solution NLC](<a href=“http://www.youtube.com/watch?v=AurMtOFh28Y&feature=channel]YouTube”>http://www.youtube.com/watch?v=AurMtOFh28Y&feature=channel) </p>
<p>This is the video I used to understand Combination & Permutation concepts</p>
<p>For permutation, you multiply everything. For ex: if you have 3 colors to chose from a total of 5 colours and order matters, then you’d have 5 possible choices for colour A, then 4 choices for B, then 3 for C, you multiply all those together to get 60 possible combinations.</p>
<p>^ Okay, so if permutation multiplies everything with matter of order, what’s the difference with combination since combination means order not important??</p>
<p>When order does not matter, just multiplying will overstate the number of possibilities.</p>
<p>For example, say you have 10 different color marbles and you want to arrange 3 of them in a line.</p>
<p>There would be 10x9x8 = 720 ways to do that. (Or 10 P 3)</p>
<p>But if you just want to know how many ways to grab a collection of 3 marbles from the 10, then order does not matter. For example, RBG and RGB would be the different line ups but the same group. In fact, every group of 3 could be arranged in 3x2x1 = 6 possible lineups.</p>
<p>So to get the number of groups, you take (10 x 9 x 8 ) / (3 x 2 x 1) = 720/6 = 120.</p>
<p>This is the same as 10 C 3 on your calculator.</p>
<p>Thank you so much.</p>