assignment2

course mth 152

I have tried to follow along but I just dont understand the questions or how you come up with the answers. I looked in the text but I am even more confused because they use different examples and go about it in a different way. I know I need to be specific but I cant tell you what it is that Im having a hard time with. It just isnt making sense to me. I dont know where to start or what to do. Im getting frustrated Help Please Connie

P??]·??w????c????????~q?assignment #002

002. Permutations, combinations, rearranging letters of words.

Liberal Arts Mathematics II

01-25-2009

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16:19:03

`questionNumber 20000

`q001. Note that there are 8 questions in this assignment.

If we choose three letter tiles from a complete set, which consists of one tile for each letter, then how many three-letter 'words' are possible ?

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RESPONSE -->

If you had a,b,c then you could make

abc, acb,bac,bca,cab,cba 6 possibilities

confidence assessment: 2

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16:20:41

`questionNumber 20000

There are 26 choices for the first tile chosen, 25 for the second and 24 for the third. The number of possible three-letter words with 3 distinct letters of the alphabet is therefore 26 * 25 * 24.

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RESPONSE -->

I was thinking three tiles not the alphabet which has 26 letters.

So you would count 26 for the first 25 for the second and 24 for the third then multiply

self critique assessment: 2

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16:28:56

`questionNumber 20000

`q002. If we choose three letter tiles from a complete set, then how many unordered collections of three letters are possible?

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RESPONSE -->

I dont understand how many is in the set. If there are just 3 and you are trying to make 3 letter words then 3*3*3= 27

confidence assessment: 1

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16:33:04

`questionNumber 20000

If the 3-tile collections are unordered there are only 1/6 as many possibilities, since there are 3 * 2 * 1 = 6 orders in which any collection could have been chosen.

Since there are 26 * 25 * 24 ways to choose the 3 tiles in order, there are thus 26 * 25 * 24 / 6 possibilities for unordered choices.

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RESPONSE -->

I dont understand any of this I wish I could be more specific but I dont understand how you know what to do. I guess Im not understanding what I m reading

self critique assessment: 1

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16:42:52

`questionNumber 20000

`q003. If we choose two balls from fifteen balls, numbered 1 - 15, from the first box of the preceding problem set, and do so without replacing the first ball chosen, we can get totals like 3 + 7 = 10, or 2 + 14 = 16, etc.. How many of the possible unordered outcomes give us a total of less than 29?

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RESPONSE -->

I think 1-15 would be 15

2-25 14

3-15 13

4-15 12

5-15 11

6-15 10

7-15 9

8-15 8

9-15 7

10-15 6

11-15 5

12-15 4

13-15 3

14+13+12+11+10+9+8+7+6+5+4+3=102

confidence assessment: 0

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16:46:19

`questionNumber 20000

The smallest possible total would be 1 + 2 = 3 and the greatest possible total would be 14 + 15 = 29. We quickly see that the only way to get a total of 29 is to have chosen 14 and 15, in either order.

Thus out of the 15 * 14 / 2 = 105 possible unordered combinations of two balls, only one gives us a total of at least 29. The remaining 104 possible combinations give us a total of less than 29.

This problem illustrates how it is sometimes easier to analyze what doesn't happen than to analyze what does. In this case we were looking for totals less than 29, but it was easier to find the number of totals that were not less than 29. Having found that number we easily found the number we were seeking.

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RESPONSE -->

So you multiply the number of balls by the number of combinations then divide by 2 because you are drawing 2 balls at a time?

self critique assessment: 1

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16:58:35

`questionNumber 20000

`q004. If we place each object in all the three boxes (one containing 15 numbered balls, another 26 letter tiles, the third seven colored rings) in a small bag and add packing so that each bag looks and feels the same as every other, and if we then thoroughly mix the contents of the three boxes into a single large box before we pick out two bags at random, how many of the possible combinations will have two rings?

How many of the possible combinations will have two tiles?

How many of the possible combinations will have a tile and a ring?

How many of the possible combinations will include a tile?

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RESPONSE -->

15balls *26 tiles*7 rings=2730

chance of 2 rings 2730/7=390/2=195

chance 2 tiles 2730/26=105/2=52

I dont understand

confidence assessment: 0

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17:06:28

`questionNumber 20000

There are a total of 7 rings. There are thus 7 ways the first bag could have contained a ring, leaving 6 ways in which the second bag could have contained a ring. It follows that 7 * 6 / 2 = 21 of the possible combinations will contain 2 rings (note that we divide by 2 because each combination could occur in two different orders).

Reasoning similarly we see that there are 26 ways the first bag could have contained a tile and 25 ways the second bag could have contained a tile, so that there are 26 * 25 / 2 = 325 possible combinations which contain 2 tiles.

Since there are 26 tiles and 7 rings, there are 26 * 7 / 2 = 91 possible two-bag combinations containing a tile and a ring.

There are a total of 15 + 26 + 7 = 48 bags, so the total number of possible two-bag combinations is 48 * 47 / 2. Since 15 + 7 = 22 of the bags do not contain tiles, there are 22 * 21 / 2 two-bag combinations with no tiles.

The number of possible combinations which do include tiles is therefore the difference 48 * 47 / 2 - 22 * 21 / 2 between the number of no-tile combinations and the total number of possible combinations.

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RESPONSE -->

I dont understand what is being asked and how you come up with knowing what to do

self critique assessment: 1

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17:16:06

`questionNumber 20000

`q005. Suppose we have mixed the contents of the three boxes as described above. If we pick five bags at random, then in how many ways can we get a ball, then two tiles, then a ring, then another ball, in that order?

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RESPONSE -->

there are 15 balls 15*14/5=42

there are26 tiles 26*25/5=130/2=65

I dont understand

confidence assessment: 0

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17:20:58

`questionNumber 20000

There are 15 bags containing balls, so there are 15 ways to get a ball on the first selection.

If a ball is chosen on the first selection, there are still 26 bags containing tiles when the second selection is made. So there are 26 ways to get a tile on the second selection.

At this point there are 25 tiles so there are 25 ways to get a tile on the third selection.

There are still 7 rings from which to select, so that there are 7 ways the fourth choice can be a ring.

Since 1 ball has been chosen already, there are 14 ways that the fifth choice can be a ball.

To get the specified choices in the indicated order, then, there are 15 * 26 * 25 * 7 * 14 ways.

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RESPONSE -->

self critique assessment: 0

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17:24:43

`questionNumber 20000

`q006. Suppose we have mixed the contents of the three boxes as described above. If we pick five bags at random, then in how many ways can we get two balls, two tiles and a ring in any order?

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RESPONSE -->

on first pick there are 15 balls

on second pick there are 26 tiles

on third pick 7 rings

15*14*26*25*7=955500

confidence assessment: 0

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17:26:04

`questionNumber 20000

There are 15 * 14 possible outcomes when 2 balls are chosen in order, and 15 * 14 / 2 possible outcomes when the order doesn't matter.

There are similarly 26 * 25 / 2 possible outcomes when 2 tiles are choose without regard for order.

There are 7 possible choices for the one ring.

Thus we have [ 15 * 14 / 2 ] * [ 26 * 25 / 2 ] * 7 ways in which to choose 2 balls, 2 tiles and a ring.

Another way to get the same result is to start with the 15 * 26 * 25 * 7 * 14 ways to choose the 2 balls, 2 tiles and one ring in a specified order, as shown in the last problem.

Whichever 2 tiles are chosen, they could have been chosen in the opposite order, so if the order of tiles doesn't matter there are only half as many possible outcomes--i.e., 15 * 26 * 25 * 7 * 14 / 2 possibilities if the order of the tiles doesn't matter that the order of the balls does.

If the order of the balls doesn't matter either, then we have half this many, or 15 * 26 * 25 * 7 * 14 / ( 2 * 2) ways. It should be easy to see why this expression is identical to the expression [ 15 * 14 / 2 ] * [ 26 * 25 / 2 ] * 7 obtained by the first analysis of this problem.

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RESPONSE -->

self critique assessment: 0

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17:32:10

`questionNumber 20000

`q007. Suppose we have mixed the contents of the three boxes as described above. If we pick five bags at random, then in how many ways can we get a collection of objects that does not contain a tile?

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RESPONSE -->

on first pick there are 26 tiles

on second there are 25

on third 24

on fourth 23

on fifth 22

on first there are also 7rings and 15 balls 7+15=22 objects other than tiles

confidence assessment: 0

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17:33:29

`questionNumber 20000

Of the 48 bags, 22 do not contain a tile. If we pick five bags at random, then there are 22 * 21 * 20 * 19 * 18 ways in which the five bags could all contain something besides a tile.

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RESPONSE -->

I dont understand

self critique assessment: 0

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17:38:15

`questionNumber 20000

`q008. Suppose the balls, tiles and rings are back in their original boxes. If we choose three balls, each time replacing the ball and thoroughly mixing the contents of the box, then two tiles, again replacing and mixing after each choice, then how many 5-character 'words' consisting of 3 numbers followed by 2 letters could be formed from the results?

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RESPONSE -->

15*14*13*12*11=360360

26*25=650

650+360360=361010

confidence assessment: 0

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17:40:06

`questionNumber 20000

Since the order of the characters makes a difference when forming 'words', the order of the choices does matter in this case.

We have 15 balls from which to choose, so that if we choose with replacement there are 15 possible outcomes for every choice of a ball.

Similarly there are 26 possible outcomes for every choice of a tile.

Since we first choose 3 balls then 2 tiles, there are 15 * 15 * 15 * 26 * 26 possible 5-character 'words'.

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RESPONSE -->

you keep multiplying by 15 because you put the ball back and you keep multiplying 26 because you put the letter back

self critique assessment: 0

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