r/MathHelp • u/theacademicBassist • 1d ago

Commutative Property of Multiplication

Hi everyone.
Taking Alg. I as a college freshman again. I'm a readmit student and always struggled with math. Currently doing homework and have 20+ attempts on the below problem:

'Use the commutative property of multiplication to write an equivalent equation:

34 + 5m'

Can't use an equal sign within the equation as it kicks back an error on the website. I've tried writing it as:

34m + 5

(34)m + 5

5(m) + 34

5m x 34

Keep getting it marked wrong. If anyone could help me better understand what I'm doing wrong I would appreciate it greatly.

6 Upvotes

100% Upvoted

19 comments sorted by

5

u/LollipopLuxray 1d ago

Can you tell me in your own words what the commutative property of multiplication is?

1

u/theacademicBassist 1d ago

Rearranging the order of any given problem and still maintaining the same answer.
So if I were to write 9 x 5, I could still get the same answer if I wrote 5 x 9.

6

u/LollipopLuxray 1d ago

Yes. But it specifically pertains to multiplication.

So you would have to rearrange only the multiplcation step of the expression.

Unfortunately i see someone else already gave you the answer soooooo

1

u/theacademicBassist 1d ago

Got it. My understanding was the entirety of the expression needed to be rewritten, not only the multiplication portion of it.

6

u/iOSCaleb 1d ago

Addition is also commutative, so you can swap the terms in addition too. But since the problem asks for an equivalent expression using the commutative property of multiplication, that’s what you need to show.

2

u/RadarTechnician51 23h ago edited 23h ago

Your attempts changed the value, to see this substitute a simple value like 2 for m, and work out the values of the expressions (don't use 0 or 1 for this because they cancel out the effect of multiplication)

A valid rearrangement of any expression should not change its value for any values of the unknowns.

1

u/juoea 23h ago

no, they are j checking whether u are able to identify which part of the expression is multiplication and what commutativity of multiplication entails.

sort of like in a word problem where they put a bunch of extra information and u have to figure out which information is relevant and how to use it

3

u/stevevdvkpe 1d ago

Commutativity isn't any arbitrary rearrangement. A commutative operation is one where the order of its two operands can be reversed. Addition is commutative because (a + b) = (b + a). The commutativity of multiplication is that (a * b) = (b * a). Most of the things you show in your post aren't commutation, but invalid rearrangements of the original expression, like changing which things are added to or multiplied by which.

3

u/SgtSausage 1d ago

Do ... do you have any idea what The  Commutative Property of Multiplication is/does?

Start there.

Read what your text has to say about it. 

'Cause your attempts demonstrat NO understanding of how it works. 

1

u/particlemanwavegirl 1d ago

In the third example, you showed the commutative property of addition. Do that, but with the multiplication.

1

u/loganpq 1d ago

Commutative sounds like commute. So your commute to work is the same as your commute back home. The expression is the same as your commute. It’s the same forwards as it is backwards.

2

u/PuzzlingDad 1d ago

You were only asked to apply the commutative property of multiplication. 

That property says you can swap the order of two things being multiplied and it doesn't affect the result. 

The two things being multiplied are 5 and m, so swap them (and only them).

34 + m(5)

If you were asked to use the commutative property of addition, then you would swap the two things being added (34 and 5m) to make 5m + 34

Now let's go through your list of answers and see why they are wrong:

34m + 5 

  • you can't swap the m which was multiplied by 5 over to the 34 which was being added. This isn't equivalent to the original expression.

(34)m + 5

  • same issue, you've just added parentheses. 

5(m) + 34

  • you've applied the commutative property of addition. While this expression is equivalent, it wasn't what you were asked to do.

5m x 34

  • Here you've changed order and changed addition into multiplication. Clearly not was asked and definitely not equivalent.

-1

u/fermat9990 1d ago

34+m(5)

This is an expression, not an equation

2

u/theacademicBassist 1d ago

thanks

2

u/francisdavey 1d ago

It's an equation if it has an "=" sign in it. I hope that helps.

1

u/theacademicBassist 21h ago

That does. I'm a readmit student and math was never my strong suit to begin with, I failed algebra multiple times in high school so most of this is water I've treaded, but not for a decade and a half. I feel stupid, but at this point in my life I'm able to recognize that I'm not going to understand it right away and that it will take time, practice, and help. So I do appreciate all the comments thus far and gone back to review the materials on this particular subject in the unit as my understanding of it was way off.

-1

u/fermat9990 1d ago

Glad to help!

1

u/localizeatp 21h ago

getting downvoted for making a true statement. wtf.