Singapore 2A pg 84?

[John'smom]

On pg 84 at the top is a section with problems written like this 469+531=, but they are in a big block. Are these suppose to be done mentally or written in a vertical way then solved? Some of them lend themselves to easy mental math (263+126), but not others (622-567). The book doesn't say what to do. I know recently there was an emphasize on writing them vertically. Just not sure what to do. Thanks for any help.

[holdinon]

I don't know if this is the right answer, but I allow my dc to work the problems in the manner that they choose once they have demonstrated they understand the concept. So I usually have them do the mental math for the lesson that is taught. Then I typically have them do it that way for a while until I know they "get it" (that may be one day or it may be a couple of weeks, depending on the kid and/or topic). But once I am confident they understand the concepts, I will then allow them to choose the way they want to solve it. Again, this may not be the way we are supposed to, but that's what we do here
Angie

[my3sons]

... I allow my dc to work the problems in the manner that they choose once they have demonstrated they understand the concept. So I usually have them do the mental math for the lesson that is taught. Then I typically have them do it that way for a while until I know they "get it" (that may be one day or it may be a couple of weeks, depending on the kid and/or topic). But once I am confident they understand the concepts, I will then allow them to choose the way they want to solve it. ...

This is what we do as well, and I have noticed that often times over time the dc can begin to tell when mental math is a viable option and when it is just easier to write the problem out and go through the steps to solve it. I might point out in the first problem you shared (469+531=) this line of mental math thinking (especially if it was taught recently in the math plans)...
9 and 1 make 10
60 and 30 make 90

10 and 90 make 100

100 and 400 and 500 make 1000
1000 is the answer!

I have noticed as the dc get older they learn that mental math is quicker and easier if it is possible. They begin to try to do the mental math, and if it becomes obvious no mental math option will be easily attained, then they write out the problem and solve it the longer way by hand. 2A is young for this kind of thinking to happen naturally, but you can help encourage it by "thinking out loud" as you go, sometimes arriving at the conclusion that mental math is easier, and sometimes arriving at the conclusion that writing it out is easier. This models the way the Singapore Textbook tries to teach several methods for solving problems, some mental math and some longer writing the problems out methods. Choosing between methods based on the type of a problem becomes easier and easier as dc get older. HTH!

In Christ,
Julie