Y5 Maths, I am so lost, can this be right?

[QuintessentiallyQS]

I think of number. I add 2753, I subtract 3572. The answer is 4839. What is my number?

I have problems getting my head around it. How is my 9 year old expected to just "get" this? I could not do this without setting up an X calculation.

Add 3572 to 4839, then subtract 2753. The answer is your number. You're just turning the sum around.

Does that make sense?

You reverse all the functions to get back to the start number.

So 4839+3572-2753= 5658

5658 is the answer

Do the stages in reverse:

Start with 4839
Add 3572
Subtract 2753

4839+3572-2753. You just reverse the operations?

It's all to do with inverse operations - undoing what has been done. Addition is the inverse of subtraction, so to undo subtract 3572, you add it to the answer (4839 + 3572 = 8411). Then you need to undo adding 2753, so subtract it (8411 - 2753). That gives you 5658, the number that was started with.

Hope this helps.

I got there in the end. It took me a while, ds was happily writing out, gluing and sticking captions for his sums. They were saying "borrow from your neighbour" and "try next door", as he had just been doing 5000-3546, etc.

The point is, are they supposed to know how to turn it all around and reverse the sums when they are 9, having just started y5?

Well it depends on the child and their current level doesn't it? Ds1 could do that easily, not quite so sure about ds2 but he's still yr4.

It's a more elaborate version of ?+4=10

He left Y4 with a 3a. I think this is too complex for him. it is all

X3X8
+2X7X
=4243

etc with x representing unknowns

Ds1 is in y7 and he never brought home this sort of stuff in Y5. (ds1 had a L6 in maths at the end of Y6)

Imagine the sum was small numbers eg less than 10 and you were talking about apples: Jane now has 3 apples. Before that she gave 2 to Tom. So you know she had 5 before. Before that Joe gave her 2 apples. So you can see she must have had 3 to start with. Does that help? My Ds who is in Y4 made sense of it!

My explanation was just to show how a child would understand about reversing the operations. The example you give with 2 unknowns in the same sum is more tricky.

I think the teacher must have set him work above his level. If this is easy peasy for a Y4 child, then I reckon she must set him less complex work.
It made my brain bleed.

I think you must be thinking like someone who knows algebra. You're overcomplicating it. It's just a simple "think of a number" type question. Like this www.primaryresources.co.uk/maths/docs/Think_of_a_number.doc

I think the issue here sounds like it is more a question of making sure your ds has been given the right tools to do the work than whether he can actually do the sum in question. If he doesn't know how to tackle the work set, that's what you need to check with the teacher.

Ah that makes sense, I am printing that out, thanks!

I think it is extra confusing working with thousands.

Bath, I have made comments about our his struggles on the sheet....

I tried my ds on this

3X8
+X7X
=479
He initially didn't see what he was supposd to do but when I asked him to just think about 8+?=9 he was then able to see it. I gave him the tools and he did the arithmetic.

Hope you get it all sorted out: I am going through something similar with my ds2 and reading!

Jesus. I couldn't do it, until it was explained how. The other example you gave with all the x's...
I had better save up for a maths tutor.
The thing with maths that I find as a very language oriented person, is that the WAY they construct sentences in maths problems really throws me. My child has the same problem. We examine the words, and stress about the meaning of them. For some people they can look at an equation and it tells them what to do. For others, it is just a jumble.
For example, if you say to me " what is a half divided by a quarter?" I have to say to myself "how many quarters are there in a half?" (2) for it to make sense. Often maths questions are just worded so oddly for people like me. And I am sure there is a reason for that, but it doesn't help!
I feel your pain quintessentially

I was struggling by year 3..

My y8 son just came home, did them in a second. I said I did not remember him having these in Y5, and he said, "I did but I did them without involving you". Oh well. Thanks for that. I appreciate being shielded!

May help to think of it with simpler numbers first:

I think of a number

I add 5 and take away 2

and I get 6

(this is effectively algebra - and may be easier to use an x for the original number)

X + 5 - 2 = 6

so what you want to get down to is x = some number

you do that by doing the same thing to both sides of the equation:

x + 5 - 2 (+ 2) = 6 (+2)

x + 5 = 8

x + 5 (-5) = 8 (-5)

x = 3

-------

so with the original problem: I think of number. I add 2753, I subtract 3572. The answer is 4839. What is my number?

Use x for the first number

x + 2753 - 3752 = 4839

x + 2753 - 3752 (+ 3752) = 4839 (+ 3752) (adding 3752 to both sides of the equation)

(the 3752s cancel each other out on the left side of the equation) so you get:

x + 2753 = 4839 + 3752

x + 2753 = 8591

x + 2753 (- 2753) = 8591 (- 2753) (subtracting 2753 from both sides of the equation)

x = 5838

So I think working on two things: converting the sentence into a mathematical equation with a letter (can be x - but can be any letter) for the unknown number you're thinking of.

then - doing the same thing to both sides of an equation (which in essence means you are maintaining the ratio between both sides)

HTH

It's firstly a comprehension exercise:
"I think of number. I add 2753, I subtract 3572. The answer is 4839. What is my number?"

"I think of a number" - it means you don't know what the number is, so you use a letter to represent it. So we have:

X

"I add 2753":

X + 2753

"I subtract 3572"

X + 2753 - 3572

"The answer is 4839" - it means 'equals 4839':

X + 2753 - 3572 = 4839

Then you just tidy it up.

X - 819 = 4839 (2753-3572=819)

X = 4839 + 819

X= 5658