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Melody

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यूजर का नामMelody
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Melody  11 Feb 2022
 #4
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mikerod111:

on negatives and positives, is there a general rule for them. I.E. negative plus negative = positive is this true for all mathematics (adding, subtracting, multiplying and dividing)?



Hi mikerod111

You've already got 2 good answers and I am about to give you a 3rd.

For multiply and divide it is very simple. If the signs are the same then the answer is positive. If the signs are different the answer is negative. See, simple.

For addition and subtraction it is a bit trickier.
Like I like Serena, I am a big user of number lines. Until you get used to it you should actually draw your number lines. I am assuming that you know how to do that.
Zero in the middle, positive numbers going off to the right, negative numbers going off to the left.

Say it is 1+6. You start at 1 then go 6 places in the positive direction and you get 7 (yea, I know, you already knew that)
Now -3+8 Start at -3 and go 8 in the positive direction and what do you get?
Now 4 - 9 start at 4 and go 9 in the negative direction and what do you get?
Now -2- 8 start at -2 and go 8 in the negative direction and what do you get?

When you get good at it you can stop drawing the number line but you should still imagine it. If you use a note book, imagine 0 in the crease of the book, the positive numbers will be on the right and the negative numbers on the left.

Now, what about those pesky + - things
for starters, If you see something like 7+(-8) it is exactly the same as 7+ - 8 (You can put the bracket in or take it away - it doesn't matter.)
That goes for 3 - - 6 = 3- (-6) as well.

Now think of a thermometer. 0 degrees is in the middle. The positive numbers are hot numbers. The negative or minus numbers are cold numbers.
Let's think about 4+ + 5 you are adding heat so it must get hotter. So it is 4+5
What about 6+-7 This time you are adding cold. So it has to get colder. It must be 6-7
And 8 - + 3. This time you are taking away heat so it has got to get colder. It must be 8-3
and lastly -1 - - 4. This time you are taking away coldness so it has to get warmer. It must be -1+4

With pluses and minuses you can also think of it like this.
If two signs are so close together that you can put a circle around them without anything getting in the way then,
if the signs are the same you replace them with a positive.
if the signs are different you replace them with a negative.

I am going to give you some questions to answer now.

1) Now -3+8 Start at -3 and go 8 in the positive direction and what do you get?
2) Now 4 - 9 start at 4 and go 9 in the negative direction and what do you get?
3) Now -2- 8 start at -2 and go 8 in the negative direction and what do you get?
4) 0-8=
5) -2-+6=
6) 1-4+(-7)=
7) -9++4 =
8) 13+(-5)=
9) -4 x 6 =
10) 3 x -6 =
11) -5 x -3=
12) 20 / -4=
13) -8 / 2=
14) -15 / -5=
15) +4 x +7=
1 Feb 2014
 #2
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deleted
1 Feb 2014
 #23
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Hi all,
Another day done
Great answers were given by Rom, I like Serena, The Guy, Expertise, Selina Marie, Right and Archhunt.
Archhunt only just joined up today. Welcome to Web2.0calc forum. We hope you like it here.

Reinout-g i have left messages at the end of your calc display posts, specially for you, oh, also on your puzzle post.

The forum is evolving very quickly now. Some of it is very exciting, other things I am a little concern about.
I don't know if it can, and I don't know whether other peoople will want it to, but I would really like this to stay fundamentally a children's forum.
There are many forums around for older people but I haven't seen many for younger people. Most of you know that it was only a week or so ago that the children and I were the only ones in this forum. ( I use the term loosely, I know that many are not children, maybe young people would be more accurate and less offensive).
I always encouraged the young people to answer, even if they got the answer wrong! I think people are much more likely to learn if they are also actively participating. Plus, teaching is a learned skill and this was giving the children a chance to learn. They responded extremely well to my guidance when it was given.

Maybe I am wrong but I expect some of the young people are already feeling 'crowded out'. (I really do not think that I am wrong). Some of the young people were giving extremely good answers on a very regular basis. I know that most of the questions will always be answered by adults and I am very genuinely grateful to all of you who have joined us. I was starting to 'burn out' and I was well aware that I needed more help. I also know that when questions are asked, the person asking is wanting a quick and accurate answer.
However, I guess I am asking you to give the children a little time to answer some of the questions themselves.
I would like the adult mathematicians to check that the answers given are correct, I see this as a very important role. Please don't think that I am aiming this at you or at any individual. We are all guity at times. I am just trying to give you an insight into what I am thinking.
Kind regards to all.
Melody.
31 Jan 2014