K-2 Math: Even & Odd 

  

Supplies: 

15 pennies | scratch paper and pencil 

  

            Learning the difference between "even" and "odd" numbers is a good way to start learning about multiplication and division, even when those math skills are still years ahead of you in school. 

  

A number is "even" if it can always be grouped by two's. Count by two's: 2, 4, 6, 8, 10, 12 . . . and so on. Those are "even" numbers. 

  

            If we say that a number is "odd," we don't mean that it is weird. :>) We mean that the number CAN'T be evenly grouped by two's. We will always have one left over if the number is "odd." So, for example, 2 and 4 are "even," but 3 and 5 are "odd." 

  

            Let's try it with some pennies. Lay out six pennies on a table or desk. Put them in two rows. How many pennies do you have in each row? (Three) Do you have any left over? (No) This shows that six is an "even" number. When we divide it into two parts, we come out "even," with nothing left over. 

  

            Now try this with seven pennies. Place them in two rows. Now how many pennies do you have in each row? (Three in one row, and four in the other) See how you don't end up with "even" rows? This shows that seven is an "odd" number - when we divide it into two parts, we have one left over. 

  

            Try this again with 10 pennies, 11, and 15. Based on results, do you think 10, 11 and 15 are "even," or "odd"? (10=even, 11=odd and 15=odd) 

  

            Now let's work a little bit with our scratch paper on some basic addition problems, to see something else interesting about "even" and "odd" numbers. 

  

            If you add two "even" numbers, do you think the answer is probably "even," or "odd"? Let's try it - 2 is "even," so what if we add 2 + 2? The answer is 4 - another "even" number. In fact, whenever you add two even numbers, the result will always be "even," too. Try it with some other even numbers you know. Can you ever come up with an "odd" answer when you add two "evens"? No. 

  

            But what if we add two "odd" numbers? Will the answer be "odd," too? No! Let's try it - 3 is an "odd" number, so let's add 3 + 3. The answer is 6 - which is an "even" number! Try adding two other "odd" numbers, and see if the answer ever comes up "odd." How about 5 + 7, or 9 + 11? Amazing! The answer is always "even." Here's the rule: adding two "odd" numbers always produces an "even" answer. 

  

            The only time you ever get an "odd" answer with addition is if you add an "even" number with an "odd" number. Let's try it: 2 is even, and 3 is odd. Let's add them: 2 + 3. The answer, 5, is "odd." 

  

            It's the same thing with subtraction. Any time you subtract an "even" number from another "even" number, the answer will be even. For example: 8 - 6 = 2 and 10 - 4 = 6. Any time you subtract an "odd" number from another "odd" number, the answer will be "even," too. Examples: 9 - 7 = 2, 5 - 3 = 2.  

  

            The only time a subtraction answer will be odd is if you subtract an "odd" number from an "even" one. For example: 10 - 7 = 3 and 8 - 7 = 1. Try a few examples of your own. 

  

            Numbers are odd, aren't they? But if you master concepts like this, you won't just be "even" with your peers in math. You'll be 'way ahead!