Can anyone figure out my grandson's Year 4 Math homework?
Can anyone figure out my grandson's Year 4 Math homework? (He is 8!)
I've attached a photo of it.
The Easy and Speedy part is fine.
However "Some subtracting" is weird - those middle numbers crossed out are on the original sheet. I can't figure out how they work. The subtractions themselves obviously work if you just ignore the crossed out numbers, and adjust for hundreds, tens and units, but why are the crossed out numbers there in the first place? They must be some sort of working out, but what? I come up with a rule that explains some of them but I can't explain them all.
Then finally there is 12, 13 and 14: "Choose three numbers to create a 3-digit number. Re-arrange the digits and subtract the smaller number from the larger number. Do this three times". This doesn't seem to me very clear. Is this what they are looking for:
Choose three numbers: 1 8 6
Re-arrange the digits and subtract the smaller number from the larger number: 8 - 6 - 1 = 1
Do this three times - just choose three numbers another two times?
Choose three numbers: 3 9 2
rearrange and subtract: 9 - 3 - 2 = 4
Choose three numbers: 3 8 2
rearrange and subtract: 8 - 3 - 2 = 3
But since these follow from 9, 10 and 11 perhaps the three numbers are similar to those? But I don't see how?
Anyway here are the original questions:
I've attached a photo of it.
The Easy and Speedy part is fine.
However "Some subtracting" is weird - those middle numbers crossed out are on the original sheet. I can't figure out how they work. The subtractions themselves obviously work if you just ignore the crossed out numbers, and adjust for hundreds, tens and units, but why are the crossed out numbers there in the first place? They must be some sort of working out, but what? I come up with a rule that explains some of them but I can't explain them all.
Then finally there is 12, 13 and 14: "Choose three numbers to create a 3-digit number. Re-arrange the digits and subtract the smaller number from the larger number. Do this three times". This doesn't seem to me very clear. Is this what they are looking for:
Choose three numbers: 1 8 6
Re-arrange the digits and subtract the smaller number from the larger number: 8 - 6 - 1 = 1
Do this three times - just choose three numbers another two times?
Choose three numbers: 3 9 2
rearrange and subtract: 9 - 3 - 2 = 4
Choose three numbers: 3 8 2
rearrange and subtract: 8 - 3 - 2 = 3
But since these follow from 9, 10 and 11 perhaps the three numbers are similar to those? But I don't see how?
Anyway here are the original questions:
ASKER CERTIFIED SOLUTION
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"Choose three numbers to create a 3-digit number. Re-arrange the digits and subtract the smaller number from the larger number. Do this three times. I take this to mean:
6, 4, 9 -> 649
Rearrange the digits.
4, 9, 6
Subtract the smaller number from the larger number.
649 - 496 = 153
This must be Common Core. The wording is obscure and poor, and the formatting is the same.
6, 4, 9 -> 649
Rearrange the digits.
4, 9, 6
Subtract the smaller number from the larger number.
649 - 496 = 153
This must be Common Core. The wording is obscure and poor, and the formatting is the same.
SOLUTION
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I think noci has the right idea on the crossed-out numbers section.
It would have been clear if it were rewritten. For example, the first one should have started with 437-163=? That would have made the basic problem much clearer.
I also think that the top numbers, 300 and 130, should be printed differently. Shaded, italics, in parentheses, or something, to show that this is what the person solving the problem adds as part of figuring it out.
It would have been clear if it were rewritten. For example, the first one should have started with 437-163=? That would have made the basic problem much clearer.
I also think that the top numbers, 300 and 130, should be printed differently. Shaded, italics, in parentheses, or something, to show that this is what the person solving the problem adds as part of figuring it out.
ASKER
Wow thanks everyone for the quick responses!!
SOLUTION
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ASKER
Thanks again - very kind of you all!
Very informative.
Do they then go on to teach what I would call the normal way of subtracting by using little marks under the line?
Do they then go on to teach what I would call the normal way of subtracting by using little marks under the line?
Though the "Some subtracting" section is very confusing as written, I think it is a reasonable way to teach the subject if it were written more clearly, such as how I suggested. I don't think the basic method is at fault; it's the very poor execution that is.
I don't at all get the point of the "choose three numbers" section. I understand what is being asked, but have no clue what the value is of that method. I guess that it is a method to force you to have something where borrowing is needed, but that seems like an odd way to do it.
I was pretty good at math, but the last section is where I'd have messed with the teacher. I'd have picked 111 as the 3-digit number!
I don't at all get the point of the "choose three numbers" section. I understand what is being asked, but have no clue what the value is of that method. I guess that it is a method to force you to have something where borrowing is needed, but that seems like an odd way to do it.
I was pretty good at math, but the last section is where I'd have messed with the teacher. I'd have picked 111 as the 3-digit number!
"I'd have picked 111 as the 3-digit number! " ROFL - sounds like fun.
I understand what is being asked and you are correct that it is a way to probably generate a situation where borrowing is required thereby creating your own problems that resemble the second section where the "borrowing" is already shown (albeit in a non-explanatory way).
If I remember my children's math books they would first have a section showing examples and explanations of problems on one page and then several pages of practice problems. Not like the old days where they had the example/explanation and then one or two problems to practice with so that everything was basically on the same page.
I understand what is being asked and you are correct that it is a way to probably generate a situation where borrowing is required thereby creating your own problems that resemble the second section where the "borrowing" is already shown (albeit in a non-explanatory way).
If I remember my children's math books they would first have a section showing examples and explanations of problems on one page and then several pages of practice problems. Not like the old days where they had the example/explanation and then one or two problems to practice with so that everything was basically on the same page.
147
rearrange = 471
471-147=?
Don't know what to do with the crossed out numbers though.