To understand what odd numbers are, we first need to understand what even numbers are. To recap, even numbers are numbers that we can split into two halves. For example, the number 2, 4, 6, and 8 can be split/divided into two: 1, 2, 3, and 4 without any numbers left over (remainder). These are what we call even numbers.
Now, odd numbers are defined as whole numbers that cannot be divided into two equal parts, thus leaving a remainder/some left over. For example, 3 and 7 cannot be divided equally into two whole numbers, therefore they are odd numbers.
Tip: A trick to spot odd numbers for bigger numbers is that if they end in 1, 3, 5, 7, or 9 (first few odd numbers) then they are odd numbers. For example, if the number 219243 ends with 3, and we know that the 3 is odd, then the number 219243 is odd.
Sample Math Problems
Question: Circle/Identify all the odd numbers in the list below:
9, 2, 20, 13, 18
Answer: The odd numbers are 9 and 13.
Revisiting the concept of what an odd number is, we know that 9 and 13 cannot be split into two equal whole numbers, therefore we know they are odd.
Question: Count the number circles and decide if it is an odd number or no
O O O O O
Answer: 5. 5 is an odd number because you can’t split/divide 5 into two equal wholes.
Question: Circle/Identify all the numbers that are not even below:
3, 2, 5, 19, 121
Answer: The numbers that are not even, basically the odd numbers, are 3, 5, 19, and 121.
For most of them, since they are smaller numbers, you can tell they are odd because they can’t be split into two equal whole halves. However, for a bigger number like 121, if you can’t tell whether its half would be equal or not, you can also refer to the last digit. The last digit in 121 is 1, and 1 is an odd number, so we can say 121 is also an odd number.
Question: Count the following circles and decide if it is an even number or an odd number.
O O O O O O O O
Answer: 8. 8 is an even number because 8 can be split into 4 and 4 (two equal wholes).
