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# Determining the Unknown Whole Number in an Addition or Subtraction Equation 1st Grade Math Worksheets

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## Definition:

In determining the unknown whole number in an addition and subtraction equation, we must understand the correlation of addition and subtraction as part of a whole.

• The biggest number is called the whole.
• The other two numbers are its parts.

Adding the parts gives the whole.
12 + 6 = 18
6 + 12 = 18

Subtracting one part from the whole gives the other part.
18 – 6 = 12
18 – 12 = 6

## Examples:

If the unknown number is the subtrahend, subtract the difference from the minuend (number before the minus sign).
15 – 11 = 4

Therefore, the unknown number is 4.
15 – 4 = 11

If the unknown number is the minuend, simply add the two known numbers.
5 + 8 = 13

Therefore, the unknown number is 13.
13 – 5 = 8

## Determining the Unknown Whole Number in an Addition or Subtraction Equation

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Each ready to use worksheet collection includes 10 activities and an answer guide. Not teaching common core standards? Don’t worry! All our worksheets are completely editable so can be tailored for your curriculum and target audience.

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