Can't figure out this SAT math problem?????

Test Preparation
1

<li>For every positive interger n, n! = n * (n-1) * (n-2) <em>…</em>1.
For example, 4! = 4 * 3 * 2 * 1= 24.</li>
</ol>

<p>What is the value of 29!/27! ?</p>

<p>I know there is a pattern but I cant figure it out. Please help</p>

2

<p>=29*28</p>

<p>the numbers 27 and down cancel out</p>

3

<p>29! = 29 x 28 x 27! So, your problem becomes:</p>

<p>(29 x 28 x 27!)/27!</p>

<p>Cancel the 27! from top and bottom, and you get:</p>

<p>29 x 28 = 712.</p>

4

<p>thanks guys</p>

5

<p>The symbol ! is known as factorial (I think that is how it is spelled). I learnt about it in advanced pre-calc class (where we learnt cool "extra" stuff). Basically, if you have a number n then n! would mean that you are multiplying n by all the numbers below n. (so if n=5 then 5!= 5<em>4</em>3<em>2</em>1) This is very useful when you are trying to figure out how many combinations or permutations are possible out of choices available. (ex. if you have 10 kids in a class, how many ways can they line up in single file?...answer: 10!)</p>

6

<p>Wisywigi, are you serious that you learned this in pre-calc? I always thought it was Algebra II material because it is essential in learning permutations and combinations which I again thought was Algebra II material.</p>

7

<p>I think it varies from school to school. We cover it in Algebra II, and review in Precalculus.</p>

8

<p>Yea, factorials is Algebra II.</p>

<p>:)</p>

9

<p>
[quote]
29 x 28 = 712

[/quote]
</p>

<p>29 x 28 = 812</p>

10

<p>you can also do this problem on the calculator</p>

11

<p>How can you do it on the calculator faster than 29x28? o_O</p>

12

<p>if you did not grasp the concept, you can find the symbol(!) by pushing the "math" button and then scroll to the right to the probability(PRB) category. number 4 is the exclamation point.</p>

13

<p>It would be faster if you typed in 29 x 28 on the calculator than doing 29 x 28 by hand. I think that would be the only time the calculator would be faster, unless you've memorized what 29 x 28 is.</p>

14

<p>Hahah. I think quitejaded meant how could doing the ENTIRE problem on the calculator be faster than simplifying it first and then doing 29 x 28 on the calculator. Because that WOULD be faster.</p>

15

<p>Yup, I'm serious. Combinations and permutations were in my textbook this year and our curriculum is based mostly on our textbook. The book is called Advanced Mathematics Precalculus with Discrete Mathematics and Data Analysis, and is published by McDougal Littell Inc.</p>