Math 2B Add/Sub Money Part NEED HELP!

[E2Mom]

Guys, just ran into a bit of a snag today, and I'm hoping the veterans can help me out. This is my first year using Singapore (just in case that matters), and for the most part, I really like it. I like the concepts, etc. SO...we are on Adding and Subtracting money from pages 40 to 48ish Textbook 2B. So, I am wondering if my daughter NEEDS to know how to ANALYZE each problem to determine WHICH TYPE of math she'll be using for that problem (i.e. "Mental" vs. "Basic/long add/subtracting"). She can DO all of the mental methods, but can't figure out WHICH one to use. I kinda came up with about 3-4 ways of doing them mentally that they taught in those pages. 1) Just adding dollars and then cents, 2) Separating the figures to help, and 3) Rounding the ones in the 90 cents range to $1, etc. So, what I need to know is HOW important is it for her to know WHICH method to use? Should I just TELL her which method, or HELP her decide, or should she be able to determine this on her own? So, give me some wisdom fellow sisters!

[kvmck]

I am no math expert and don't know if this will be much help! When my son was doing these problems, he too would figure them out in his mind with no problem. I would then have him write it down and figure it out using addition and subtraction some of the time just so I knew he could do that. I would also ask him to tell me how he figured out the answer in his mind... and very often he and I would use a different mental method to arrive at the same answer! If I saw his method was obviously "inferior" to mine I would explain to him the "easier" way (i.e. $4.30 + $.99=... the best way is to round up and then subtract a penny.... so if he was trying to "separate out" then I would lead him to the rounding up way...) I guess I felt like one of the main points of this particular money section was that he would learn to use all the methods and to be able to decide for himself which one works best for him in each situation.


I'm interested to hear insights from other moms as well.