Subtraction Games

Subtraction Games that will teach the strategy of:

Half Facts

Half Facts are when you subtract a number from exactly half of itself (10-5=5).

The best way to understand this is to know the Doubles strategy when adding. You can think backwards: So, 10 - 5 becomes 5+?=10.

1. Making associations with things that are memorable to your child is very effective. If you have already made associations when learning the Doubles strategy you've done the work.

So....if you picked the association of "days of the week" (7 days) to learn Double facts, your child can think....

"1 week plus 1 week equals 14 days". You can use the same concept to remember your half facts. "2 weeks is 14 days" if you "subtract 1 week (7 days) you will have 1 week (7) left" 14-7=7.

Some ideas for making associations:

2's: shoes, eyes, ears, nostrils, arms, legs

3's: traffic lights, triangle edges, tricycles, 3 wise men, peanut

butter sandwich

4's: car wheels, seasons, members of the Beatles

5's: fingers, toes, minute hand on the clock

6's: half dozen eggs, 6 pack of soda

7's: days of the week, points in a football game, the Harry Potter

series (7 books in all), 7 continents

8's: octopus legs, octagon, spider legs

9's: tic tac toe game, lives of a cat, fingers (if you lose one in an

accident-kids love this one)

2. In order to see the relationship between Half facts and Doubles you will need to practice finding halves of numbers. Think about ordinary things you share between 2 people throughout the day: cookies, carrots, pizza, bagels ,etc. Although not terribly healthy "French Fry Facts" are fun. Next time your eating french fries, dump them out and count them, decide what half would be. Eat half. Now split that in half, eat, etc.

3. Back to the old 10/20-Frame: If your child needs more support you can practice using two 10 frames side by side. 14-7.... Fill 10 frames up with 14 markers, take away 7. The process of doing this will build a sense of how the numbers fit together.

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