Odd and even numbers
8 pencils, paired up: 4 neat pairs, nothing left over. 7 pencils, paired up: 3 pairs, and one pencil left over.
A number is even if its dots pair up completely. Like 2, 4, 6, 8, 10. A number is odd if one dot is always left over. Like 1, 3, 5, 7, 9. Zero is even too — no dots to pair.
Step 1 of 3
- 3 has one leftover dot. 5 has one leftover dot too.
- The two leftovers pair up with each other.
- 3 + 5 = 8. No dot is left over. Even.
Even plus even: no leftover. Even. Odd plus even: one leftover. Odd. Odd plus odd: the two leftovers pair up. Even.
Slide two numbers in the lab. Look at the leftover dots.
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