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# Determine the Unknown Number in the Addition or Subtraction Equation (up to 20).

These worksheets support the following Common Core State Standard:

CCSS.Math.Content.1.OA.D.8

Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 = ? - 3, 6 + 6 = ?.

Publisher: National Governors Association Center for Best Practices, Council of Chief State School Officers, Washington D.C.

(Page last edited 10/16/2017)

There are 100 worksheets available on this topic. Click on the thumbnails below to preview and download the worksheets.

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