Question

Use counters to subtract $2-(-1).$
You start with:

You subtract:

Which picture shows the difference?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

We are trying to calculate 2 - (-1).
Start with 2 positive counters

You would like to take away 1 negative counter. However, it's not possible to take away 1 negative counter, because there aren't any negative counters in the first group.

You can fix this problem by adding 1 pair of positive and negative counters to the first group, (A pair of positive and negative couters equals to 0) so that you have the 1 negative counter that is needed.

Now take away 1 negative counter:
3 positive counters remain.
$\therefore 2-(-1)=3$