Is my theory right?

Test Preparation SAT Preparation
1

<p>I've developed a theory very hastily, I think it's wrong. Can someone check my logic?</p>

<p>Alright, there are 8 different fruits. How many combinations of three is it possible to make?</p>

<p>My reasoning?</p>

<p>8 possible for the first space, 7 for the next, 6 for the last.</p>

<p>8x7x6=336.</p>

<p>HOWEVER, some combinations will be done over again, and must be deducted.</p>

<p>So . . . 8 possible spaces, three fruits . . . . 3/8.</p>

<p>3/8 * 336 = 126</p>

<p>336 - 126 = 210.</p>

<p>210 possible combinations. Is this correct? If not, what is the proper method?</p>

2

<p>I got 56...</p>

3

<p>Could you explain so I know the method?</p>

4

<p>56 is right (8!)/(3!5!)</p>

5

<p>(8 x 7 x 6) / (3 x 2) </p>

<p>since there are 3 spaces, you start off with 8 x 7 x 6
then you divide by the factorial of the number of spaces
(I'm not sure if this is the right method either)</p>

6

<p>You are right, but doesn't that theory exist already?</p>

7

<p>why do you have to divide by the second factorial?? If your using the counting principle, you wouldn't need to...</p>

<p>oh nevermind, i got it "combinations"....theres a button on your calculator that does it in seconds..</p>

<p>plus collegeboard math doesn't go into combinations and permutations, the only principle you have to know is counting principle</p>

8

<p>So then the answer would be 8 x 7 x 6 / 3!, correct?</p>

9

<p>Yes, and lazy, what is this counting principle that you keep refering to?</p>