ScribePost for March 3, 2009

Today in math class, we did "Number of the Day" with the number as "7791.692".


Afterwards teacher guy went up to the projector, pushed a button, turned it on, made a noise, and showed us some notes to take down.


The notes were on:




















First we had to take down some words and their definitions.

Outcome - One possible result of a probability experiment.

Favorable Outcome - A successful result in a probability experiment.


Then he gave us an example with some questions.

"The tiles "S, N, O, W," are placed in a bag.

First question: What is the probability of drawing the letter "W" from the bag?

Another way to write that question is P(W)
(P stands for probability)

P(W) =
favorable outcomes
----------------------------
possible outcomes

So then most of us thought, Hmm, 4 letters, and we only want one of the letters so it must be:

P(W) = 1
---
4

Another way of expressing that is
25%
or
1 : 4




Second Question: What is the probability of drawing a S or an O from the bag? P(S or O) =
favorable outcomes
------------------------
possible outcomes

Now you had to think, 4 letters and we want 2 of them so what are the chances of getting them?

It was, of course,:
2 1
-- simplified as --
4 2
50%
2 : 4


P(S or O) = 1 P(S or O) = 50%
-- or
2 P(S or O) = 1 : 2

Third Question: What is the probability of drawing a consonant from the bag?
P(consonant) =
favorable outcomes
----------------------------
possible outcomes

Since in class, like around 10 people don't know what a consonant is so click that link for the definition.

Anyway, if you know what a consonant is, this is easy since there are 3 consonants, "S, N, and W". Three favorable outcomes, and four in total, you should know this by now:

P(consonant) = 3
--
4

Another way to write this is
75%
or
3 : 4


Fourth and last Question for "S.N.O.W.": What is the probability of drawing a "B" from the bag?
P(B) =
favorable outcome
----------------------------
possible outcomes
Really simple if you listened, there are 4 letters, you want to draw "B", but there is no "B", so there is ZERO chance of drawing it. This is not out of 4 because now there are 5 choices:

P(B) - 0
--
5

Another way to write this is
0%
or
0 : 5








After all that stuff, we were given ANOTHER problem.

A bag contains 10 marbles. Show the probability of the following events as a fraction, a ratio, and a percentage.

1. 3 Blue
2. 6 Red
3. 3. Green
   

A. What is the probability of drawing a red marble?
P(red marble)=
favorable outcomes
----------------------------
possible outcomes

There are 6 red marbles, 10 marbles in total, this is obviously 3 over 5 simplified.
3
--
5
or
60%
or
6 : 10

B. What is the probability of selection a red or blue or green marble?

P(R or B or G)
favorable outcomes
----------------------------
possible outcomes

There are ONLY red, blue, and green marbles in this bag so that makes it a 10 out of 10 chance. -.- STEPHANIE -.-
P(R or B or G)
1
--
1
or
100%
or
1 : 1


C. What is the probability of NOT selecting a red?
P(B or G)=
favorable outcomes
----------------------------
possible outcomes

Your trying not to get a red, so you have to find the probability of all the rest of the outcomes. So add up the amount of blues and greens to get your numerator and the total of all the outcomes as your denominator.
P(B or G)=
4 2
-- simplified --
10 5
or
20%
or
4 : 10

Finally its over!


Homework:

Here are the letters you have to work with:

M.O.U.N.T.A.I.N.

A.What is the probability of drawing the letter "N"?

B. What is the probability of drawing a consonant?


C. What is the probability of drawing a letter?


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