Crystal Call

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course mth 151

Feb 276:40 pm

Assignment 11" "011. How many triangles?

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Question: `q001. . There are 6 questions in this set.

Draw four points unconnected in a square pattern (i.e., four points that could be connected to form a square). From each of the points, draw a straight line to each of the other points. How many lines did you draw?

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Your solution: I drew 6 lines

confidence rating #$&*: now that I read the given solution, the obvious solution is 12 lines as I didn’t think of the over lapping lines

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Given Solution:

Each corner of the square will connected to each of the other three corners, so from each corner you would have drawn three lines. Since there are four corners, had you followed the instructions precisely you would have drawn 4 * 3 = 12 lines. However each of these lines will be identical with another line you would have drawn, since for any two corners you would be drawing a line from the first to the second then another overlapping line from the second to the first. Therefore you might have said that there are 6 lines.

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Self-critique (if necessary):

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Self-critique Rating: ok

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Question: `q002. How many triangles are there in the figure you drew?

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Your solution: I counted 8 triangles

confidence rating #$&*:

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Given Solution: You should have a total of 8 triangles. The diagonals divide the square up into 4 small triangles. Each diagonal also divides the square into 2 larger triangles. Since there are 2 diagonals there are 4 larger triangles. The 4 small triangles and the 4 larger triangles total 8 triangles.

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Self-critique (if necessary):

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Self-critique Rating: ok

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Question: `q003. The lines you drew should form a square with its two diagonals. Label the corners of the square A, B, C and D, going in order around the square, and label the center where the diagonals cross E. Now list all possible combinations of 3 of the letters A, B, C, D, E (note: combinations don't care about order, so A D E is the same as D A E or E A D or any other combination of these same three letters, so list each possible combination only once. That is, if you list for example ADE you won't list DAE).

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Your solution:

AEB BCD

BEC ADB

DEC DBC

AEC ABD

ADC ABC

confidence rating #$&*:

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given Solution: The easiest way to list these sequences is alphabetically: ABC, ABD, ABE all start with AB; then ACD and ACE start with AC and ADE starts with AD. This is a list of all possible combinations containing A. We next list all possible remaining combinations containing B: BCD, BCE and BDE. Then we write down CDE, the only remaining combination containing C. We thus have the 10 combinations ABC, ABD, ABE, ACD, ACE, ADE, BCD, BCE, BDE, CDE.

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Self-critique (if necessary):

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Self-critique Rating: ok

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Question: `q004. Of the 10 combinations ABC, ABD, ABE, ACD, ACE, ADE, BCD, BCE, BDE, CDE, which form triangles on your figure?

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Your solution: I got 8 triangles

BEC CED

DEA AEB

ACB BDC

ADB ACD

confidence rating #$&*:

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Given Solution: ABC forms a large triangle from A to B to C and back to A. The same is true of ABD, ACD and BCD. These are the large triangles in the figure. ACE and BDE form straight lines, not triangles. ABE, ADE, BCE and CDE form small triangles. Thus of the 10 possible combinations of labeled points, we find the 4 large triangles and the 4 small triangles we saw earlier, in addition to 2 straight lines which do not for triangles. Since any triangle in the figure must be labeled by three of the five points A, B, C, D, E, we see that these are the only triangles that can be formed.

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Self-critique (if necessary):

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Question: `q005. Sketch the same figure as before, but without the line segment from A to B. Now how may triangles are there?

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Your solution: 5 triangles

ACD ADE

BCE BCE

CDE

confidence rating #$&*:

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Given Solution:

Any possible triangle must still come from the list ABC, ABD, ABE, ACD, ACE, ADE, BCD, BCE, BDE, CDE. We again see that ACE and BDE form straight lines so do not count as triangles. Now ABC, ABD and ABE do not form triangles because the line segment AB is now missing. This leaves us the five triangles ACD, ADE, BCE, BCE and CDE.

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Question: `q006. How many triangles in the original figure do not have point C as a vertex?

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Your solution: I only counted 3 triangles that didn’t have C as a vertex

confidence rating #$&*:

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Crystal Call

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course Mth 151

Feb 27, 20148:07 p.m.

Assignment 12" "012. The common sense of logic.

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Question: `q001. Note that there are 5 questions in this assignment.

Suppose I tell you 'If it rains today, I'll give you $100.' Under which of the following circumstances can you claim that I was not telling the truth?

1. It rains and I give you $100.

2. It rains and I don't give you $100.

3. It doesn't rain and I give you $100.

4. I doesn't rain and I don't give you $100.

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Your solution:

2. It rains and I don’t give you $100

confidence rating #$&*:

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Given Solution:

I said what would happen under a certain condition. In situation #2, that condition is fulfilled and what I said would happen doesn't happen. Therefore in situation #2 it is clear that I wasn't telling the truth.

In situation #3, the condition that I addressed isn't fulfilled so no matter what happens I can't be accused of not telling the truth. I said what would happen if rains. No matter what happens, if it doesn't rain what I said cannot be held against me.

It should be clear to anybody that situation #1 is exactly what you would expect, and that situation #4 is just would you would probably expect from my statement in the event that it doesn't rain, so nobody would say that this situation violates my claim to truthfulness.

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Self-critique (if necessary):

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Self-critique Rating:

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Question: `q002. Suppose that tell you 'It will rain today and I will give you $100'. Under which of the following circumstances can you claim that I was not telling the truth?

1. It rains and I give you $100.

2. It rains and I don't give you $100.

3. It doesn't rain and I give you $100.

4. It doesn't rain and I don't give you $100.

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Your solution:

2, 3, & 4 you could claim that there was a lie told

confidence rating #$&*:

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Given Solution:

It should be clear that situation #1 completely fulfills the conditions of my statement. Both of the things that I say will happen do happen.

In situation #2, it rains but you don't get the $100. I said two things were going to happen and one of them didn't. In that case you would have to say that I wasn't telling truth.

In situation #3, again one of the things I say is going to happen does but the other doesn't, so again you would have to say that I wasn't telling truth.

In situation #4, neither of the things I say will happen does and certainly it would have to be said that I wasn't telling truth.

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Self-critique (if necessary):

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Self-critique Rating:

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Question: `q003. Suppose that tell you 'It will rain today or I will give you $100, but not both'. Under which of the following circumstances can you claim that I was not telling the truth?

1. It rains and I give you $100.

2. It rains and I don't give you $100.

3. It doesn't rain and I give you $100.

4. I doesn't rain and I don't give you $100.

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Your solution:

1 and 4 you could say there was a lie told

confidence rating #$&*:

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Given Solution:

In situations 2 and 3, one of the things happens and the other doesn't, so you would not be able to say that I wasn't telling the truth. However in situation 1, both things happen, which I said wouldn't be the case; and in situation 4 neither thing happens. In both of these situations you would have to say that I was not telling truth.

STUDENT COMMENT:

:im not sure if I don’t understand or if there is just a typo present it would seem to me that 2 and 3 show that one situation was fulfilled and not the other which is what you said would happen

INSTRUCTOR RESPONSE:

In situation 1, I both things happen. However my statement include the phrase 'but not both'.

In situation 4, neither thing happens. My statement said that one would happen.

So in both situations 1 and 4, my statement fails to be true.

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Self-critique (if necessary):

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Self-critique Rating:

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Question: `q004. Suppose that tell you 'It will rain today or I will give you $100'. Under which of the following circumstances can you claim that I was not telling the truth?

1. It rains and I give you $100.

2. It rains and I don't give you $100.

3. It doesn't rain and I give you $100.

4. I doesn't rain and I don't give you $100.

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Your solution:

2,3,4

confidence rating #$&*:

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Given Solution:

At first this might seem to be the same as the preceding problem. But in the preceding problem we specifically said '... but not both.' In this case that qualification was not made. Therefore we have regard the statement as true as long as at least one of the conditions is fulfilled. This is certainly the case for situation 1: both conditions are true we can certainly say that at least one is true. So in situation #1 we have to regard the present statement as true. So situation #1 would not be included among those in which I could be accused of not telling the truth.

STUDENT COMMENT:

Im not sure weather 2 was included in the statement that were not true

INSTRUCTOR RESPONSE:

In situation 2 one of the conditions was fulfilled, satisfying the original 'or' statement. So situation 2 doesn't contradict the original statement.

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Self-critique (if necessary):

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Self-critique Rating:

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Question: `q005. Suppose I make the statement 'The stock market will rise today or I will buy your dinner'. If the stock market does not rise today, is there something I can do or fail to do that would enable you to logically conclude that I wasn't telling the truth? If it is possible, specify what it is that I must do or fail to do. If it is not possible, explain why.

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Your solution:

The stock market does not rise and I do not buy you dinner would make the me a liar since neither requirements was met.

confidence rating #$&*:

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Self-critique Rating:

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Question: `q005. Suppose I make the statement 'The stock market will rise today or I will buy your dinner'. If the stock market does not rise today, is there something I can do or fail to do that would enable you to logically conclude that I wasn't telling the truth? If it is possible, specify what it is that I must do or fail to do. If it is not possible, explain why.

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Your solution:

The stock market does not rise and I do not buy you dinner would make the me a liar since neither requirements was met.

confidence rating #$&*:

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Self-critique Rating:

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