## Common Core State Standards for Mathematics

Grade(s) 1 resources related to the following standard:
Operations and Algebraic Thinking
6. Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 — 4 = 13 — 3 — 1 = 10 — 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 — 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).

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This interactive Flash applet contains a progressive range of exercises to sharpen mental math and recall of number facts. Levels include one-digit addition and subtraction within 20, two-digit addition and subtraction within 100, and multiplication up to x5 and x10. The goal is to complete 10 correctly as quickly as possible. An incorrect answer deletes a point, discouraging guessing. At the end of each round the applet reports the time taken and the number of errors.
Activity, Interactive Media
Grade Level: 1, 2, 3, 4
This interactive and animated Flash book, the first by collaborators Greg Tang and Harry Briggs, presents 16 riddles that use clever, visual tricks to challenge children to add and eventually multiply numbers in efficient groups. The best solutions are the least obvious, which teaches children to be more thoughtful, strategic, and open-minded.
Activity, Interactive Media, Illustration, Video
This applet counts according to the starting number, the increment of change, and the speed selected by the user. It can be used flexibly by students or by the teacher as part of a lesson. Its applications include skip counting (forward and backward), exploring number patterns, integer addition and subtraction, decimals, and division. Suggestions for instructional use are provided.
Interactive Media
Grade Level: K, 1, 2, 3, 4, 5
This iOS app provides students in grades K-2 with practice counting, writing numerals, addition and subtraction. The user can select the grade level and adjust the time of practice; the app then generates a selection of activities from the base six activities of the app. At the end of the practice the app asks for feedback on the level of difficulty in order to make adjustments for the next practice session.
Activity, Interactive Media, Mobile App