negative/positive numbers

Discussion in 'Middle School / Junior High' started by angeluv73, Nov 26, 2007.

  1. angeluv73

    angeluv73 Rookie

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    Nov 26, 2007

    My 7th graders still have issues adding and subtracting neg & positive #'s. How can I teach this AGAIN so they wont have trouble any more? I know some of you MUSt have a great way to solidify this in their brains! Ive done the number line stuff, Ive done the red chips and yellow chips....anymore ideas??????:help:
     
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  3. uclalum

    uclalum Groupie

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    Nov 26, 2007

    I do the things you have already mentioned. They also make their own number line. Hmmm, perhaps buy a vertical number line. It might make more sense (to some) than a horizontal number line.
     
  4. Aliceacc

    Aliceacc Multitudinous

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    Nov 27, 2007

    My most concrete explanation is with money:
    positive numbers are money you have; negatives are money you owe (or charge or whatever.)

    SO: -5+7: you owe $5 but earn $7. After you pay off your debt you HAVE $2. -5+7=2
     
  5. Upsadaisy

    Upsadaisy Moderator

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    Nov 27, 2007

    When all else fails, follow the rules:

    Addition of:

    Different signs: + and -
    Subtract the two numbers and choose the sign of the one with the larger absolute value

    Same signs: + and +, - and -
    Add and keep the sign

    That's it.

    The rule for subtraction is even easier:
    DON'T. Reverse the sign of the second number, reverse the subtraction sign to addition. Then follow the rules for adding integers.
     
  6. mmswm

    mmswm Moderator

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    Nov 29, 2007

    lets say the problem is -17 + 8. I ask, suppose you borrowed 17 bucks from Juan last week and you swore to him you'd pay him back today. But, today you only gave him 8 dollars, do you still owe him money? Now, what if you came in with 20 bucks? Do you have any money left over? After using this type of analogy a couple of times my students rarely have any more issues.
     
  7. Carmen13

    Carmen13 Groupie

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    Nov 30, 2007

    I use the own and loan too. I think it works better than the other strategies I tried .
     
  8. Carmen13

    Carmen13 Groupie

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    Nov 30, 2007

  9. WaterfallLady

    WaterfallLady Enthusiast

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    Dec 1, 2007

    Here is what I do for my kids: (well, the whole 6 weeks I had math)

    I draw a ladder on our magnetic white board. The ladder is drawn with the bottom part (anything under 0) being underground. Kids start with their behavior on five. Each time the majority of the class is acting up they go down. They understand when they are "underground" they owe me a point. Then, I have a number line and I add how many points they got by moving a clothespin with their class period marked on it. If they owe me points (below ground or negative) I move backwards on the number line.

    I've been told my kids are not developmentally ready to understand negative numbers due to their disabilities but almost all of them have been able to understand this way.
     
  10. CanadianTeacher

    CanadianTeacher Groupie

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    Dec 2, 2007

    Use visuals. Use something of two different colours like poker chips. One colour represents positives and the other colour represents negatives. Show them how the positive and negatives cancel each other out. then they can see what they have at the end. Once they do this a while and start to make connections, they shouldn't need the chips anymore. It worked great for me last year.
     
  11. Mrs.Rhinochunks

    Mrs.Rhinochunks Companion

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    Dec 2, 2007

    I have found that a football field analogy makes sense for boys quite often. instead of a 6- yard line in the middle it is the 0 yard line and there is no goal post on either end-the field just continues forever. i ask, if you are in the red teams area (-20 yards) and you get the ball and carry it (+50 yards) into your territory, what yard line are you on? or... if you start at the -20 and end up on your 30, how far did you carry it?
     
  12. RLucas

    RLucas Rookie

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    Dec 2, 2007

    I also use the money concept and it works well - I have high schoolers that until we use money and the owing have never figured out positives and negatives. When we multiply and divide - I use when a good thing happens to a good person that is bad, when a good person goes to jail that is bad, when a bad person goes to jail that is good. Two positives = a positive, a positive and negative = a negative and two negatives = a positive. In my school where majority know someone in jail, it is easier for them to grasp.
     
  13. mathteacher07

    mathteacher07 New Member

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    Dec 2, 2007

    Here is the solution

    "The Battle" I have taught the "Battle" with seventh graders that show a problem on the board such as
    -8+3 Indicate the negative in red on one side and blue for positive.
    Show 8 of the negative signs and 3 of the positive and tell the students that they are battling each other when they are opposite. The teacher crosses out the negative and positive until there is no more positive or negative left and in this case the answer will be -5. It's hard to explain on here, but let's see if it works for your students.

    Jennifer:2up:
     
  14. ~~Pam~~

    ~~Pam~~ Companion

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    Dec 3, 2007

    In addition to the horizontal number line, I also used a vertical thermometer. I related the integers to money, temperature, stock prices (gain and loss) and just continue to reinforce the skills as we have moved into other units. On computer lab days, I always allow about 10-15 minutes at the end of the period for students to go to www.xpmath.com and play any of the number sense games related to integers. They LOVE them!!
     

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