Help your child succeed with subtracting negative numbers
For this exercise you will need red and white counters. 10 or 15 of each color is a good number to start with. As problems get more complex you may need more. You can buy these counters or easily make them as a project with your child. Poster board cut into circles work just fine also to add more of a remembrance as to which is negative and positive you can tell the child if i give you money it makes you what (happy) so you can draw a smiley face on each white counter and then the same goes for the negative, if i take away your money it makes you (angry/sad) then you can put angry or sad faces on the red counters. the faces can help a child who doesn't associate the color red with being negative.
Subtraction with negative numbers can be difficult to comprehend especially to a child who cannot grasp what is happening to the numbers in the problems. The activity subtraction of integers using colored counters helps students to understand how to subtract with negatives much easier. This also shows them why a positive number minus a negative number equals a larger positive number. In this activity we used red and white counters to symbolize the negative numbers (red) and the positive numbers (white). This activity really helps students who are visual or hands on learners and need that extra to help them understand what exactly is being represented in the problem.
So to start problem -6 – (-2) = -4, with the counters this is shown by 6 red counters and taking away two of them leaving 4 red counters. The red counters are negative and the problem requires you to take away two negatives leaving you with four negatives. Next problem is 7 – (-2) = 9. To show this you have seven white or positive counters, you can’t take away two negative, or red counters from all white or positive counters, so you add two red counters and so the red counters don’t just cancel out two of the white counters you add two more white counters to balance them out. Now you can take away two negatives or red counters out of the group, thus leaving you with nine white counters. The next problem (-10) – 12 = -22, you start with ten red or negative counters and you can’t take away twelve positives (white) from ten negatives (red). So you add twelve positives and twelve negatives, now you can take away twelve positives away and that leaves you with 22 negative counters. So these shows how, when you are subtracting you can end up with a larger number.
The NCTM standard that this activity meets is algebra standard. This instructional should enable students to represent and analyze mathematical situations and structures using algebraic symbols, use mathematical models o represent and understand quantitative relationships, and analyze change in various contexts. This activity teaches a student to represent the negative and positive numbers in problems and how to read algebraic symbols like the plus sign or negative verses the subtraction symbol. It also teaches them to analyze the problems and structures using symbols like the red and white counters. Also in this standard students will need to be able to use mathematical models to represent and understand quantitative relationships. This activity teaches students how to use models, the red and white counters, to represent the positive and negative numbers in these math problems and will allow them to use that in their future. In their future this technique could help them with money, balancing their check book or business and understanding the stock markets ups and downs.
The second NCTM standard that this activity meets is the connections standard. This enables students to recognize and use connections among mathematical ideas, understand how mathematical ideas interconnect and build on one another to produce and coherent whole. And recognize and apply mathematics in contexts outside of mathematics. What this means is students will be able to use this activity to help them understand how a bill negatively affects their positive or already negative bank account. Also how bills (negatives) and paychecks (positives) can build and how interest on their savings works for or against them. Relating negative and positive numbers to counters is a visual aid and helps students to see what happens to the actual numbers, where they came from and not just memorize some rules.