Are there any games to help with learning this? I don't see how the "Go To The Dump" game can help, since it's only for making 10, as I understand.

Is the "2-fives" strategy more important, or more helpful, than the "making a ten" strategy? If so, can you tell me how and why that is? Does it have to do with algebra later, or geometry, or what?

I can barely do the "2-fives" strategy myself, and I don't know how to reinforce it with ds. All the strategies so far (9's, 8's, and 2-fives) really are just different ways of "making 10", right? But the 9's and 8's tricks are easier with a shorter thinking process than the 2-fives, because you're just adding 3 addends, basically, but with the 2-fives you're adding 4 addends and need an extra mid-step.

For example:
7+8=

8's trick:
5+2+8=
5+10=15

2-fives:
5+2+5+3=
5+5+2+3=
10+5+15


What about bigger problems, like this? What is the best way RS suggests to do it?
67 + 74=
like this, separating the 10s?:
60 + 70 + 7 + 4 =
50 + 10 + 50 + 20 + 7 + 1 + 3 =
100 + 30 + 10 + 1 =
100 + 40 + 1 = 141

On those bigger problems in Level B, lessons 70ish, I'm not sure what strategies to suggest for ds, or to reinforce, or which ones RS is trying to focus on, especially when the lesson doesn't make any specific suggestions for which strategy to use.

thanks for you help,
Teresa

Hi Teresa,

You are correct in stating that the 9's and 8's strategies are different ways of making 10. Making 10 is the easiest way to solve an answer with numbers over 8. The 2 fives can be easier when adding, for instance, 6 and 6 because there are two fives, which is 10 with 2 more, which makes 12. The other piece to this is the ability to "see" the abacus in your head. If you can "see" what 6 + 6 looks like in your head than you will "see" the color difference knowing that there are two fives there plus two more.

However, please remember that these are strategies that you are given to use if they work for you as in if you assimilate them into your thinking process. They are not intended to cause frustration and may in time make sense as you move forward.

As far as how does go to the dump help? It help in the sense of inviting your child to use the abacus and to "see" the quantities that make 10 an reasoning as to the why behind it. Also another easy game to play is addition war where the quantities will add up to a number over 10 thus having your child needing to consider the different strategies for adding, which can include the 2-fives strategy.

I hope this helps answer your question as well as alleviate confusion.

Thanks for your questions.

Sincerely, Rosine