Wednesday, March 18, 2009

Today during class we did our "Pre-test" for our current unit of probability. The pre-test prepares us for our upcomming unit test which takes place tomorrow March 19. The format of our pre-test was 2 multiple choice questions, 2 short answer questions, and 1 3-step problem. We were given about 35-40 minutes to write our pre-test and after that Mr. K split us up into groups to compare answers. After about ten minutes of comparing answers, Mr. K went over the questions and showed us step by step how it came out to the answer.

In my group there were a couple a questions that stumpted my group members and I, but now I understand why and how we got the answer.

Here is one question that we didn't quite get right..

Using the word FOOD, find the probability that an arrangement of this word will begin with the two O's if all the letters are used. Correct to the nearest hundreth.

So to start off, you need to make sure that the two O's are stuck together at the front of the four letter combination. A way that Mr. K would refer it to would be "take the two O's and put them in a bag."

And this is what the 4 letter word combination can look like..

The first 1 stands for the 2 O's which are "stuck together," they are first because the question requires for them to be at the front of the four letter combination. The 2 stands for the choice of either F or D. And the last 1 stands for the left over of the previous two. (Say I choose F for the second space, then the last space would be a D and vice versa.)

So now you are required to multiply 1 by 2 by 1 in order to find out the number of ways for the combination. The answer is 2.

Now you take the the amount of ways that the four letter word can be rearranged(2 differnt ways) and you divide it by 4 factorial(representing the total number of letters) divided by 2 factorial(representing the 2 O's)

You would do it like so..

The result would be 2/12 then would reduce into 1/6, and because the question says around to the nearest hundreth, you must express the faction into a decimal which is 0.17.

* JUST A REMINDER * our unit test is tomorrow!
For further review Mr. K posted up extra questions.

I choose Kayla for the next scribe!


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