Do students practice sums to 12 or 18?

Julie asks:
For addition and subtraction, do students practice with sums through 12’s or 18’s? For example, 12+ 6. Thanks.

Dr. Don answers:
Hi Julie!  The Rocket Math basic program (and basic subscription) is 1s through 9s both for addition and subtraction–meaning students practice single digit sums up to 9+9 and subtracting single digit numbers up to 18-9. The Rocket Math Universal subscription provides access to the Add to 20 program which includes 7 + 12 and the Subtract from 20 program which includes 19-7. The Add to 20 and Subtract from 20 programs were added because the Common Core recommends students be fluent at adding and subtracting these numbers mentally without manipulatives.

As the picture above suggests if a student knows 7+2 is 9, it doesn’t take much to learn that 7+12 is 19. However, the Add to 20 program will give students practice with those facts. Especially for students who master the 1s through 9s facts quickly, these additional programs will cement in the basic facts learning by extending them to some teen number addends. Conversely, for students who struggle with learning the 1s though 9s facts, these extra facts should be considered optional or enrichment, in my opinion.

So I recommend first graders learn the 1s-9s addition first followed by the Add to 20. Then in second grade the 1s though 9s subtraction followed by Subtract from 20. Not everyone will get through both, but kids will see the connections doing the higher problems if they have completed 1s through 9s first. They won’t need to practice to Z before they see the patterns and can do the problems without much practice. I am happy to provide this extra option for those who can take advantage of it.

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