Text Assignment 3-4

course Mth 151

΂Yүr~}assignment #015

015. `query 15

College Algebra

05-15-2009

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10:57:42

Query 3.4.6 write converse, inverse, contrapositive of ' milk contains calcium'

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RESPONSE -->

Converse: If calcium is contained in it then it is milk

Inverse:If it is not milk it does not contain calcium

Contrapositive: if it is not calcium contained in it then it is not milk

confidence assessment: 2

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10:58:06

** 'Milk contains calcium' can be put into p -> q form as 'if it's milk then it contains calcium'.

The converse of p -> q is q -> p, which would be 'if it contains calcium then it's milk'

The inverse of p -> q is ~p -> ~q, which would be 'if it's not milk then it doesn't contain calcium'.

The contrapositive of p -> q is ~q -> ~p, which would be 'if it doesn't contain calcium then it's not milk'.

Note how the original statement and the contrapositive say the same thing, and how the inverse and the converse say the same thing.

NOTE ON ANOTHER STATEMENT: If the statement is 'if it ain't broke don't fix it:

Converse: If you don't fix it, then it ain't broke

Inverse: If it's broke, then fix it.

Contrapositive: If you fix it, then it's broke. **

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RESPONSE -->

Pretty close

self critique assessment: 3

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11:00:22

Query 3.4.18 state the contrapositive of 'if the square of the natural number is even, then the natural number is even.' Using examples decide whether both are truth or false.

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RESPONSE -->

If the natural number is not even then the spuare of a natural number is not even.

The first statement is false and the contrapostive is true

You can figure this out by doing a couple quick mathematical calculations

confidence assessment: 3

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11:00:49

** The statement is of the form p -> q with p = 'square of nat number is even' and q = 'nat number is even'.

The contrapositive of p -> q is ~q -> ~p, which in this case would read 'if a natural number isn't even then its square isn't even'.

STUDENT RESPONSE WITH SOMEWHAT PICKY BUT IMPORTANT INSTRUCTOR CORRECTION: if the natural number isn't even , then the square of a natural numbewr isn't even

Good. More precisely: if the natural number isn't even , then the square of THAT natural number isn't even. To say that the square of a natural number isn't even doesn't necessarily refer to the given uneven natural number.

COMMON ERROR WITH INSTRUCTOR COMMENT: The natural number is not even, if the square of a natural number is not even. ex.-3^2=9,5^2=25 This statement is true.

** You have stated the inverse ~p -> ~q. It doesn't matter that the 'if' is in the second half of your sentence, the 'if' in your statement still goes with ~p when it should go with ~q. COMMON ERROR WITH INSTRUCTOR COMMENT: If the natural number is not even, then the square of the natural number is not even.

This statement does not involve square roots. It addresses only squares. And 26 isn't the square of a natural number. **

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RESPONSE -->

Ok.

self critique assessment: 3

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11:01:23

Explain how you used examples to determine whether both statements are true or both false.

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RESPONSE -->

I used examples such as were shown before with 3 and 5 squared

confidence assessment: 3

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11:01:30

** The first statement said that if the square of a natural number is even then the natural number is even. For example, 36 is the square of 6, 144 is the square of 12, 256 is the square of 16. These examples make us tend to believe that the statement is true.

The contrapositive says that if the natural number is even then its square isn't even. For example, the square of the odd number 7 is 49, which is not an even number. The square of the odd number 13 is 169, which is not an even number. This and similar examples will convince us that this statement is true. **

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RESPONSE -->

Ok

self critique assessment: 3

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11:01:53

Explain why either both statements must be true, or both must be false.

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RESPONSE -->

They are compound... they build upon each other

confidence assessment: 3

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11:02:01

** The reason is that the truth tables for the statement and its contrapositive are identical, so if one is true the other is true and if one is false the other must be false. **

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RESPONSE -->

Ok

self critique assessment: 3

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11:02:34

Query 3.4.24 write 'all whole numbers are integers' in form 'if p then q'.

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RESPONSE -->

If it is a whole number then it is an integer

confidence assessment: 3

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11:02:41

** p could be 'it's a whole number' and q would then be 'it's an integer'. The statement would be 'if it's a whole number then it's an integer'. **

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RESPONSE -->

Got it :-)

self critique assessment: 3

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11:03:25

Query 3.4.30 same for ' principal hires more only if board approves

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RESPONSE -->

If the principal hires more teachers thenthe school board approved

confidence assessment: 3

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11:03:37

COMMON ERROR WITH INSTRUCTOR COMMENT: If the principal will hire more teachers, then the school board would approve.

INSTRUCTOR COMMENT:

p only if q is the same as if p then q; should be 'if the principle hires, the school board approved' **

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RESPONSE -->

got it :-)

self critique assessment: 3

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11:04:07

Query 3.4.48 true or false: 6 * 2 = 14 iff 9 + 7 neg= 16.

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RESPONSE -->

False

confidence assessment: 2

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11:04:26

** Both statments are false, but the compound statement is true.

The compound statement 'p if and only if q' is equivalent to 'if p then q, AND if q then p'.

This compound statement is true because p and q are both false, so 'if p then q' and 'if q then p' are both of form F -> F and therefore true **

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RESPONSE -->

Oh its asking if the compound statement is true. I didn't catch that

self critique assessment: 3

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11:06:11

Query 3.4.55 contrary or consistent: ' this number is an integer. This number is irrational.'

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RESPONSE -->

contrary

confidence assessment: 2

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11:06:24

**Any integer n can be expressed in the form p / q as n / 1. So all integers are rational.

Irrational numbers are defined as those numbers which are not rational.

So the statements are indeed contrary-it is impossible for a number to be both an integer and irrational. **

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RESPONSE -->

Got it

self critique assessment: 3

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&#Very good responses. Let me know if you have questions. &#