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Math Mammoth (Gr 3): Order of Operation. Was it introduced in Gr 2? Does this seem difficult to you?


morningcoffee
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Ds is doing math mammoth grade 3 and the concept of doing the operation in the parenthesis is explained. There are 6 questions that follow which are obviously designed to show that the presence of a parenthesis will affect the final answer (eg. 20 – 6 – 2 = ______; 20 – (6 – 2) = ______). 

 

Then the student is asked to write an expression to match each instruction:

 

"First add 40 and 50, then

subtract that sum from 120.â€

 

“First add 70 and 50, then

subtract 90 from that sum.â€

 

Ds found this quite a leap. Should we go back to math mammoth grade two and see if this is introduced and practiced earlier?  

 

 

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I don't think parentheses are introduced sooner.

 

Is the trouble with translating words into numerical symbols? Maybe you can walk him through that with a few.

 

"First add 40 and 50--OK, let's put that in parentheses to show that we do it first: (40+50);

 

Now it says we need to subtract that from 120 so let's write the 120 in front and then a subtraction sign:

 

120-(40+50)"

 

Then solve.

 

If the large numbers are making it feel difficult try substituting small numbers--so you end up with 12-(4+5)

Edited by maize
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The same thing is introduced in MEP 3.  DS had a series of problems that had all the numbers and signs in the same order, but parentheses put in at different points in each problem to show the difference.

For word problems like you mentioned, we found it easier to work on a whiteboard first, then paper.  It allows for him to translate the words better if all he has to do is wipe and rewrite as he processes the information.

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I don't recall seeing it in grade two. It is covered again in grade 4 and used extensively to develop the steps for the multiplication algorithm. I wouldn't stress it in grade 3. If you get to grade 4 and it is still a struggle, you can break it down and add review at that point. Maybe just doing a simple problem each day at the beginning of math time would help.

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I don't think parentheses are introduced sooner.

Is the trouble with translating words into numerical symbols? Maybe you can walk him through that with a few.

 

"First add 40 and 50--OK, let's put that in parentheses to show that we do it first: (40+50);

 

Now it says we need to subtract that from 120 so let's write the 120 in front and then a subtraction sign:

 

120-(40+50)"

 

Then solve.

 

If the large numbers are making it feel difficult try substituting small numbers--so you end up with 12-(4+5)

 

Yes, it was the word to number translation that was hard.  I did walk him through it but your explanation is much better than what I managed  :001_smile:

Edited by morningcoffee
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