Fact Strategies for Addition and Subtraction



Fact Strategies for Addition and Subtraction

Plus One and Minus One, Plus Two Minus Two

• Addition - this strategy involves starting with a number and counting on 1 or 2.

Example: 7 + 2 = 9; think “7…8,9”

• Subtraction – this strategy involves counting back 1 or 2 from a number.

Example: 9 – 2 = 7; think “9…8,7”

Plus Zero and Minus Zero

• Addition – this strategy involves recalling that if one addend is 0, the sum is always the

other number. Example: 8 + 0 = 8

• Subtraction – this strategy involves recalling that if 0 is subtracted from a number, the

number does not change. Example: 9 – 0 = 9

Combinations of Ten

• Addition – this strategy involves recalling all the different combinations of 10.

Examples: 0 + 10, 1+ 9, 2 + 8, 3 + 7, 4 + 6, 5 + 5.

• Subtraction – this strategy involves recalling all the different combinations of 10

Example: 10 – 7 = 3; think “7 plus what equals 10? (answer 3)”

Plus Ten and Minus Ten

• Addition – this strategy involves building teen numbers and recognizing that the number added to ten is in the one’s place for the teen number.

Example: 10 + 5 = 15; think “since I am adding 10 + 5 , the answer will have 1 ten and 5 ones (answer 15)”

• Subtraction – this strategy involves recalling the parts that make the teen numbers.

Example: 15 – 10 = 5: think “10 plus what equals 15? (answer 5)”

Plus Nine and Minus Nine

• Addition – there are two strategies that help children learn these facts.

1. This strategy involves recalling what 10 + the number equals and going down 1.

Example: 9 + 7 = ___; think “10 + 7 = 17, so go down one for 9 + 7 = 16.”

2. This strategy involves recalling that the one’s digit in the sum is

always one less that the number added to nine.

Example: 9 + 7 = 16; think “1 less than 7 is 6, so the answer is 16.”

• Subtraction – this strategy involves recalling what the answer would be if the problem was subtracting 10, and then add 1 more to the answer.

Example: think “14 – 10 = 4, so 14 – 9 = 5.”

Doubles Plus and Minus

• Addition – this strategy involves recognizing that the two addends are the same. Most children learn the doubles facts quickly. These facts can be practiced with dominoes and also real life examples. Example: Fingers (5 + 5 = 10), Egg carton (6 + 6 = 12),

Days in two weeks (7 + 7 = 14), Crayons in the row of a box (8 + 8 = 16)….

• Subtraction – this strategy involves recalling the addition doubles facts.

Example: 14 – 7 = ____; think “7 plus what equals 14? (answer 7)”

Doubles Plus and Minus One

• Addition – the strategy involves recalling the double fact and adding 1 more. It is also called the “near-double” strategy. Example: 6 + 7 = ___; think “6 + 6 = 12,

so 6 + 7 = (12 + 1) or 13”

• Subtraction –this strategy involves recalling the addition double fact and near-double fact. Example: 13 – 6 = ___; think “ 6 plus what equals 13? 6 + 6 = 12 and 6 + 7 = 13,

so 13 – 6 = 7”

Doubles Plus and Minus Two

• Addition – there are two strategies that could be used for these problems.

1. This strategy involves recalling that when numbers are two apart, the sum is double the middle number. Example: 5 + 7 = ___; think “6 is between 5 and 7 and 6 + 6 = 12,

so 5 + 7 = 12.”

2. This strategy involves doubling the lower addend and then adding two to the sum. Example: 5 + 7 = ____; think “ 5 + 5 = 10, so 5 + 7 = (5 + 5) + 2 or 12.”

• Subtraction – this strategy involves recalling the addition double fact and doubles plus two fact. Example: 12 – 5 = ___; think “ 5 plus what equals 12? 5 + 5 = 10 and

(5 + 5) + 2 = 12, so 12 – 5 = 7”

Rote

Rote facts are ones that have no specific strategy. Children usually develop their own strategy for these facts. After all of the other strategies are mastered, there are only five remaining rote facts. They are: 6 + 3, 7 + 4, 8 + 3, 8 + 4, 8 + 5, and their subtraction inverses. Children will often relate these facts to combinations of ten.

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