5th grade order of operations

[Mr.joe]

Hey guys I just joined because I can't help my son with his homework. He is totally frustrated and so am I. This should be very easy and I am almost certainly making a simple mistake. Ignore the actions on the third problem because they are obviously in the wrong place.

I think I know order if operation, but can't make this work please help.

 

[Deleted member 4993]

Hey guys I just joined because I can't help my son with his homework. He is totally frustrated and so am I. This should be very easy and I am almost certainly making a simple mistake. Ignore the actions on the third problem because they are obviously in the wrong place.

I think I know order if operation, but can't make this work please help. View attachment 21841

Since you did work for C) - I'll do that problem for you:

-7 + 11 + 4 + 2 = 10

You need to show us several tries for A) & B) - each.

These are just "keep on working" problem - fun for some people but torture for others.

 

[Mr.joe]

Oh. Wow. I didn't even consider changing a number to negative. Thanks so much! Seriously

 

[Dr.Peterson]

Hey guys I just joined because I can't help my son with his homework. He is totally frustrated and so am I. This should be very easy and I am almost certainly making a simple mistake. Ignore the actions on the third problem because they are obviously in the wrong place.

I think I know order if operation, but can't make this work please help.

As SK said, all you can do here, ultimately, is to try and try and try; there is no formal method by which you can directly find the answer. And sometimes they can be as frustrating for me as for you. My opinion has long been that these should not be presented as homework, but as puzzles to do for fun.

Of course, I've seen enough of these to know a few tricks. For (A), I first tried adding the numbers and got 40. We need to decrease that by 23, and I know that changing a + to a - would change the result by an even number, so something besides addition and subtraction is needed. Multiplication makes numbers that are mostly too big (I tried a few); division will usually produce fractions, so that isn't likely. But you might want to see what happens if you do the simplest possible division ...

My "try adding and change some to subtraction" works for (C): the sum 7 + 11 + 4 + 2 = 24, which you have to decrease by 14. Do you see how to get to the answer from there?

 

[Mr.joe]

As SK said, all you can do here, ultimately, is to try and try and try; there is no formal method by which you can directly find the answer. And sometimes they can be as frustrating for me as for you. My opinion has long been that these should not be presented as homework, but as puzzles to do for fun.

Of course, I've seen enough of these to know a few tricks. For (A), I first tried adding the numbers and got 40. We need to decrease that by 23, and I know that changing a + to a - would change the result by an even number, so something besides addition and subtraction is needed. Multiplication makes numbers that are mostly too big (I tried a few); division will usually produce fractions, so that isn't likely. But you might want to see what happens if you do the simplest possible division ...

My "try adding and change some to subtraction" works for (C): the sum 7 + 11 + 4 + 2 = 24, which you have to decrease by 14. Do you see how to get to the answer from there?

Honestly I don't immediately see an answer other than the one posted above. I would imagine there is more than a single answer. After many attempts at (a) I started believing the problem was actually broken and didn't have a correct solution. I was just happy to see a fast reply so that I can at least believe it is possible. A bit embarrassing to confess that I am struggling with a ten year olds school work

 

[Deleted member 4993]

Honestly I don't immediately see an answer other than the one posted above. I would imagine there is more than a single answer. After many attempts at (a) I started believing the problem was actually broken and didn't have a correct solution. I was just happy to see a fast reply so that I can at least believe it is possible. A bit embarrassing to confess that I am struggling with a ten year olds school work

Oh come on!!.. I got the second one (B) just mentally. Get 12 and add 6 to it to get 18.

 

[Mr.joe]

Oh come on!!.. I got the second one (B) just mentally. Get 12 and add 6 to it to get 18.

Ok, you win. I kinda expected these to seem easy after the fact. (30-18)+ (24÷4)= 18.
I spent more time trying the first one than the other 2, but... thanks again.

 

[Steven G]

15 / (8-5) + 12 = 17

 

[Mr.joe]

Thanks guys, I have it now.

 

[Steven G]

7 + 11 - 4*2 = 10

These problem can be frustrated especially when it comes from 5th grade math.

Being able to do this or not being able to do these in my opinion means nothing. Either you tried the correct combination or you did not. The trick that Dr Peterson mentioned about changing the sign of a number will make the sum decrease by an even number is a common trick and does help sometimes. But again it mostly trial and error.

Go take a break with your son and laugh about how you did not see the correct combinations. Hopefully he is good with order of operation problems so just tell him all that matters is that he is good at it!