Even and Odd Numbers
Even numbers can be split into pairs with nothing left over: 46 is even. Odd numbers always leave one extra: 73 is odd. For any number, big or small, the last digit is all you need to check.
What are even and odd numbers?
Put 8 counters into pairs: you get 4 pairs and nothing is left over, so 8 is even. Put 7 counters into pairs: 3 pairs and 1 counter without a partner, so 7 is odd. An even number can also be shared fairly between two people.
Even numbers: 0, 2, 4, 6, 8, 10, 12 … Odd numbers: 1, 3, 5, 7, 9, 11, 13 … On the number line they take turns: even, odd, even, odd.
The last-digit rule
For a big number there is no need to count pairs. Look at the ones digit only:
- Even if the last digit is 0, 2, 4, 6 or 8: 30, 52, 94, 100.
- Odd if the last digit is 1, 3, 5, 7 or 9: 21, 47, 65, 99.
Is 58 even or odd?
- The last digit is 8.
- 8 is one of the even digits 0, 2, 4, 6, 8.
Answer: even
Is 85 even or odd?
- The last digit is 5.
- The 8 tens do not matter; only the ones digit counts.
Answer: odd
Why only the last digit? Every ten is 5 pairs, so the tens never leave a counter over. Only the ones can.
Adding even and odd numbers
- even + even = even: 4 + 6 = 10
- odd + odd = even: 3 + 5 = 8 (the two extra counters make a new pair)
- even + odd = odd: 6 + 7 = 13
- Every double is even: 7 + 7 = 14, 25 + 25 = 50.
Without adding, is 27 + 35 even or odd?
- 27 is odd and 35 is odd.
- odd + odd = even.
- Check: 27 + 35 = 62, which ends in 2.
Answer: even
List of even and odd numbers to 100
Even numbers from 1 to 100: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100.
Odd numbers from 1 to 100: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99.
Counting by 2s from 2 gives the even numbers; counting by 2s from 1 gives the odd numbers.
Examples
42
57
12, 14, 16, __, __
Practice problems with answers
Solve these problems on paper or out loud, then check the answer key. The online practice and the printable worksheet give a new set every time.
- 31 is ___ (even / odd)
- 26, 28, 30, ___
- 73 is ___ (even / odd)
- 9 is ___ (even / odd)
- 40, 42, 44, ___
- 77, 79, 81, ___
- 70 is ___ (even / odd)
- 77 is ___ (even / odd)
Show answers
- odd
- 32
- odd
- odd
- 46
- 83
- even
- odd
Common mistakes
- Looking at the tens digit instead of the ones: 34 is even because it ends in 4, and 43 is odd because it ends in 3.
- Thinking that zero is neither even nor odd. Zero is even, just like 10, 20 and 30.
- Expecting odd + odd to be odd: 5 + 7 = 12 is even.
- Counting by 2s from the wrong start: 1, 3, 5, 7 are odd, but 2, 4, 6, 8 are even.
Questions parents ask
How do you know if a number is even or odd?
Look at the last digit. If it is 0, 2, 4, 6 or 8, the number is even; if it is 1, 3, 5, 7 or 9, it is odd. 46 is even, 73 is odd.
Is 0 an even number?
Yes. Zero splits into two equal groups (0 and 0) with nothing left over, and it fits the pattern even, odd, even: 0, 1, 2.
How many even numbers are there from 1 to 100?
There are 50 even numbers (2 to 100) and 50 odd numbers (1 to 99).
Why do second graders learn even and odd numbers?
It builds on pairs and doubles and prepares for multiplication, because the even numbers are exactly the answers in the 2 times table. The Common Core standard 2.OA.C.3 asks children to tell whether a group of up to 20 objects is even or odd.