Order of 5 + <3> in II18/<3> is 6

  • Thread starter aliciaislol
  • Start date
Yes, that's correct. So the order of 5+<3> is 6. In summary, the order of the element 5 + <3> in the quotient group II18/ <3> is 6.
  • #1
aliciaislol
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Homework Statement


Find the order of the element 5 + <3> in the quotient group II18/ <3>.


Homework Equations


II18 = {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18}
<3> = {3,6,9,12,15,18}
5 + <3> = {5,8,11,14,17,2}
order is the number of elements

The Attempt at a Solution


I am thinking this II18/ <3> equals {3,6,9,12,15,18} and I have to find the order of that plus 5.

So I got the order as 6.
 
Last edited:
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  • #2
Find the order of the element 5 + <3> in the quotient group II18/ <3>.

I assume II18 means Z18, i.e. integers mod 18 under addition mod 18.

II18 = {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18}
<3> = {3,6,9,12,15,18}
5 + <3> = {5,8,11,14,17,2}
OK, and 18=0=the identity in II18.

order is the number of elements

Not in this case. Order of a group is the number of elements. Order of an element is the smallest positive integer n such that a^n=aa...a=identity (in multiplicative notation), i.e. such that na=a+a+...+a=identity (in additive notation, which applies to this example). You have to find the order of the element 5 + <3> in the group II18/<3>
I am thinking this II18/ <3> equals {3,6,9,12,15,18} and I have to find the order of that plus 5.

So I got the order as 6.

This part is all wrong. II18/ <3> equals {<3>,1+<3>,2+<3>}. The identity in this group is <3>, or maybe you call it 18+<3>.

Add the element 5+<3> to itself repeatedly until you get the identity <3>. Note that 5+<3> = 2+<3>. How many times did you add it to itself? That is, what was the smallest positive integer n such that n times 5+<3> equals the identity <3>? That n is your answer.
 
  • #3
so I did that and I came up with:
0+<3> = {0,3,6,9,12,15}
1+<3> = {1,4,7,10,13,16}
2+<3> = {2,5,8,11,14,17}
3+<3> = {3,6,9,12,15,0}
4+<3> = {4.7.10.13.16.1}
5+<3> = {5,8,11,14,17,2}
So I get that 0 & 3 are tha same, 1&4 are the same and 2&5 are the same.
So I have to do n(5+<3>)= {3,6,9,12,15,0}? b/c nothin times 2 will give me 15.
 
Last edited:

1. What is the meaning of "Order of 5 + <3> in II18/<3> is 6"?

This statement refers to the mathematical concept of order of operations, where the expression inside the parentheses (5 + <3>) is evaluated first, followed by the division (II18/<3>), resulting in a final answer of 6.

2. How is the order of operations determined in this expression?

In mathematics, the standard order of operations is PEMDAS, which stands for Parentheses, Exponents, Multiplication and Division (from left to right), and Addition and Subtraction (from left to right). This means that in the given expression, the addition inside the parentheses is evaluated first, followed by the division.

3. Why is the order of operations important in mathematics?

The order of operations is important because it dictates the sequence in which mathematical expressions should be evaluated. Following the correct order ensures that everyone arrives at the same answer when solving a given expression. Without it, there would be ambiguity and confusion in mathematical calculations.

4. What happens if the order of operations is not followed?

If the order of operations is not followed, the result of a mathematical expression may be incorrect. For example, if the expression 5 + 3 x 2 is evaluated without following the order of operations, the result will be 16 instead of the correct answer of 11. This is because multiplication should be performed before addition.

5. Can the order of operations be changed in this expression?

No, the order of operations cannot be changed in this expression. It is a fundamental rule in mathematics that must be followed in order to get the correct answer. However, the order of operations can be changed if parentheses are used to group certain parts of the expression differently.

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