Vanishing sums and almost-vanishing
You learn that if you take away everything, 0 is left, and if you take away almost everything, 1 is left.
How to work it out
- Do you take away the same number? Then everything is gone and you have 0 left.
- Do you take away one less? Then exactly 1 is left.
15 − 15 = ?
- Take away everything.
- 15 − 15 = 0.
Another example
23 − 22 = ?
- Take away almost everything (one less than 23).
- 23 − 22 = 1.