Do United Set have to be written in order from smallest to largest number?

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karinakarina

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[FONT=&quot]Math question on my 6th grader's test: [/FONT]

[FONT=&quot]A U B [/FONT]

[FONT=&quot]A={2, 9} [/FONT]
[FONT=&quot]B={8} [/FONT]

[FONT=&quot]My daughter wrote {2, 9, 8} [/FONT]

[FONT=&quot]The teacher marked it wrong and wrote the correct answer as: {2, 8, 9} [/FONT]

[FONT=&quot]So united sets must be written in order from smallest to largest? Is that correct? Can someone confirm? Thank you![/FONT]
 
karinakarina said:
Math question on my 6th grader's test:

A U B

A={2, 9}
B={8}

My daughter wrote {2, 9, 8}

The teacher marked it wrong and wrote the correct answer as: {2, 8, 9}

So united sets must be written in order from smallest to largest? Is that correct? Can someone confirm? Thank you!
Click to expand...
No, a set does not have to be defined in numerical order. A set may not even consist of numbers so how can you order it numerically. Nor can a set of complex numbers be ordered.

https://en.m.wikipedia.org/wiki/Set_(mathematics)

However, I have seen people define sets to be ordered. Moreover, it is useful to show orderable sets in their "natural" order. Unless the instructions specified to write down the set in ascending numerical order, your daughter was correct, and the teacher was wrong. It will not be the first time that she will have to put up with someone in authority making a mistake.
 
karinakarina said:
Math question on my 6th grader's test:

A U B

A={2, 9}
B={8}

My daughter wrote {2, 9, 8}

The teacher marked it wrong and wrote the correct answer as: {2, 8, 9}

So united sets must be written in order from smallest to largest? Is that correct? Can someone confirm? Thank you!
Click to expand...

sets in general do not follow numerical order. the elements (members of a set) can be written in any order because sets can also have letters as their elements, or even pictures. so maybe better double check the teacher's instruction. If not stated to order them numerically, or the teacher didn't specifically instruct the class to do so, then the teacher must have overlooked your child's answer. Please double check :)
 
jtayag0622 said:
sets in general do not follow numerical order. the elements (members of a set) can be written in any order because sets can also have letters as their elements, or even pictures. so maybe better double check the teacher's instruction. If not stated to order them numerically, or the teacher didn't specifically instruct the class to do so, then the teacher must have overlooked your child's answer. Please double check :)
Click to expand...
The problem was posted over 3 months ago; the OP still has only 1 post.
So you're losing your time...
 
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