Add integers using counters

key notes:

▶️ Pairs made up of a positive counter and a negative counter have a value of zero.

Learn with an example

Use counters to add -3 + 1.

You start with:

You add:

Which picture shows the sum?

You are trying to calculate -1 + 4.

Start out with 1 negative counter, which represents -1:

You are trying to calculate -3 + 1.

Start out with 3 negative counters, which represent -3:

Now add 1 positive counter:

Since pairs made up of a positive counter and a negative counter have a value of zero, cross them out.

2 negative counters remain:

So -3 + 1 = -2.

Use counters to add 4 + 2.

You start with:

Which picture shows the sum?

You are trying to calculate 4 + 2.

Start out with 4 positive counters, which represent 4:

Since the counters are all positive, just count them. There are 6 positive counters, so 4 + 2 = 6.

Use counters to add -2 + -2.

You start with:

Which picture shows the sum?

You are trying to calculate -2 + -2.

Start out with 2 negative counters, which represent -2:

Since the counters are all negative, just count them. There are 4 negative counters, so –2 + –2 = –4.

Let’s practice!🖊️