Which way does it jump?
Every one of these is one jump along a line. The two signs in front of the number decide nothing except which way you face, including the case where they turn you round twice.
8 − (−3) = 11
- The jump
- 8 − (−3)
- Same as
- 8 + 3
- The jump goes
- right
Drag either end of the jump along the line.
Add it or take it away
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Where it usually goes wrong
“Two minuses make a plus” gets applied by reflex, without ever having been a picture of anything, so it also gets applied where it does not belong. Here the two signs mean two different jobs: one says which number, the other says which way to face. 8 − (−3) turns you round twice, which is why it lands at 11.
Try this
- Set up 8 − (−3) and watch the jump face right. It is the same jump as 8 + 3, and that is a result rather than a rule.
- Now do 8 + (−3) and watch it face the other way.
- Start at a negative number and take away a positive. The jump goes further from zero, which is where the answers stop looking like arithmetic and start needing the line.
Where this goes next
Every sign error in algebra is this one, arriving later and with letters on it.