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Minus number

  1. Jan 20, 2009 #1
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solutionMy teacher said when we take away a number bigger than a nuther number we have to do a minus number. 5-7=something


    I don't get what she means.
     
  2. jcsd
  3. Jan 20, 2009 #2

    symbolipoint

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    Think of the numbers paired to points on a number line. Increasing to the right are the positive numbers; increasing to the left are the NEGATIVE numbers. directly at the "start" of the positive numbers and the negative numbers is the one point which they share. That is the number ZERO.

    You can perform simple arithmetic using this number line. If you begin with 5, and then SUBTRACT 7, this means you start at 5 and then move 7 units to the left. Which point (coordinate) on the number line does this take you? You should have located the number, NEGATIVE 2, which you would write as: -2
    Notice also that this is 2 units to the left side of ZERO.
     
  4. Jan 20, 2009 #3
    symbilpoint i don't get what you mean like whats a number line and coordinate means what?ok so i put -2 <negetive 2> so 5-7=-2 ok but there is a nuther 1 I have to do. number 2 says find 3-7+2


    I don't get it becous when I use my fingers I don't no what to do when all put all the fingers downe. Theres not enuff fingers if I use my other hand to put them up so can you help if you tell me how to use the fingers if their is a minus number like if I put my other fingers up or what.

    Thx!
     
  5. Jan 21, 2009 #4

    symbolipoint

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    Runescapedude, do not use your fingers! Use a number line. You can take yourself through the calculation and see where the expression, 3-7+2, will be on the number line.

    Young students in grade 1 usually learn to add and subtract whole numbers both on a number line and on their fingers. At that grade level, the number line starts at zero, and counts upward to the right. Those students in grade 1 only use whole numbers, and they are only the positive numbers.

    Now that you are learning to subtract larger numbers from smaller numbers, you need to extend the number line toward the left of zero to use the negative numbers.
     
  6. Jan 21, 2009 #5

    Mark44

    Staff: Mentor

    What if you had $25 in your checking account, but you wrote a check for $30? (Banks of course don't like you to do this.)
     
  7. Jan 21, 2009 #6
    I don't get what you mean like starts at zero and counts upward to the right. Im in yeer 3 but no 1 like's the teacher becous she puts me on deetenshen..... She put on the bord this thing with lines but other lines 2 with ulot of number's and she torks fast and torked to fast for me to rite but evriwon gets it beter.


    I don't get $ and what is the check thing mean. I have a bank with mor dolers than my frend Jack becous he has 20 dolers and I have mor. Do you have mor.
     
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