Maths - adding/subtracting negative positive numbers

[annielouise]

Hi
I saw a wonderful explanation on how to add and subtract negative and positive numbers in one of the comments, I believe by someone home educating but I can't find it now, even with an advanced search. Does it ring a bell with anyone? If I'd realised it was the next topic that my son was going to do I'd have printed it off. The explanation included concepts like borrowing if I remember rightly. Wish I'd paid more attention now.

can't remember the thread, but I made a number line with both positive and negative numbers, then used the same "jumping frogs" they used when they started adding and taking away in the beginning.

this thread ?

throckenholt - this is the one, it's the section by DyslexiaTeach - brilliant. Thanks so much. If I'd remember the rest of the thread - BIDMAS and BODMAS - I might have found it through advanced search. Thanks for locating it and thanks too to ShrinkingViolet, a number line is great but actually getting your head round some of the negatives and positives is hard, if not impossible, for me too.

I remembered reading it and that it had the word bodmas in it so I searched on that

Hope it helps.

There was a really good physical demonstration of negative numbers with holes in the ground in the channel 4 Dispatches, Kids Don't Count episode 2, which you can still watch on 4OD, if you have time.

I completely forgot the word BODMAS and must admit I don't ever remember being taught that at school (I did O level maths). Will watch the 4 Dispatches programme if I can find it. Thanks again.

If you can't find it. The DCs went outside and dug holes. The hole was the negative number and the pile of soil was the positive number. Therefore if you had -3 and wanted to add +5 you had to take 5 of the piles of soil and you filled in the 3 holes and had 2 piles left over, therefore -3 add 5 = 2.

sometimes it helps to think of the minus as a direction. Assume all positive numbers have an invisible + and head in a give direction (eg up, or to the right), then a negative number goes in the other direction.

Adding to the number (eg x + y) makes the number bigger in the positive direction, and taking away (eg x - y ) makes it smaller, ie moves in the other direction.

So a negative number will be down or to the left.

5 - 4 is the same as 5 + -4 - ie start at 5 and move 4 back (in the other direction). The - effectively changes the direction of travel.

If that confuses you - then feel free to ignore it - but it may just help.