SAT Math question

Test Preparation SAT Preparation
1

<p>From 3rd edition, 10RS, pg 312, ques 10.
There are 3 roads from plattsville to Ocean Heights and 4 roads from Ocean heights to Bay Cove. If a person drives from plattsville to bay cove and back, passes through ocean heights in both directions, and does not travel any road twice, how many different routes for the trip are possible?</p>

<p>I know this question was already discussed in a previous thread. However, I do not understand where to start or what to multiply together. Also, how do you know that you are supposed to multiply certain #'s together in a certain way, and not in another way. Basically my main question is how do you know how to solve this kind of probability problem. I am really bad at probabilities and I NEVER know what #'s to use and how to multiply/add them.</p>

2

<p>On the way up, there are 3 possible roads to OH, and 4 roads to BC. On the way back, one road in each leg has already been taken, and the person does not travel the same road twice, so there are only 3 possibilities from BC to OH and only 2 possible routes from OH to P. You simply multiply these possibilities to find the number of combinations.</p>

<p>3 x 4 x (4-1) x (3-1)
= 3 x 4 x 3 x 2
= 72</p>

3

<p>COPY AND PASTE THIS INTO WORD-CONCISE,COMPREHENSIBLE-I HIGHLY RECOMMEND. DEALS WITH PROBABILITY,PERMUTATION AND COMBINATION QUESTIONS. YOU READ THIS, AND YOU’LL NEVER GET ANOHER ONE OF THESE TYPES OF QUESTIONS WRONG AGAIN:</p>

<p><a href=“http://home.comcast.net/~dave.kim/prob.doc[/url]”>http://home.comcast.net/~dave.kim/prob.doc&lt;/a&gt;&lt;/p&gt;