Charge Model for Integer Addition

Pre-Algebra · Axiom Academy

Charge Model for Integer Addition A picture for adding positive and negative numbers: drop in charges, let the opposite ones cancel, and read off whatever is left. What does it even mean to add a negative number? "Add a positive" feels obvious — you have more. But "add a negative" trips a lot of people up: how can adding make something smaller ? The charge model gives you a picture you can trust. Think of a positive as a + charge and a negative as a − charge . One of each cancels out — a zero pair — exactly the way (+1)+(-1)=0 . Watch (+5)+(-3) play out. Five positive charges and three negative charges drop into the field. Each positive pairs off with a negative and the pair disappears — it's worth zero. When the pairing stops, whatever charges are left over are the answer. Adding integers is just this: combine the charges, throw out the zero pairs, and read what remains. Drop your own charges and cancel the pairs Add positive and negative charges in any mix you like. The net charge readout keeps a running total. When you're ready, hit Cancel pairs — every matching + / − pair vanishes at once, and the leftover charges are the sum. Each zero pair you remove is worth nothing, so it never changes the total — that's why cancelling is allowed. Set the two numbers and watch the sum appear

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