But that's not why I love Singapore math texts.
"Weimin thinks that 4.999...(the text had the proper symbol for this irrational number over the first 9 that I can't replicate) = 5. Do you agree or disagree with him. Why?"
That is why I love Singapore math texts. Catherine called me over because she didn't understand it. We discussed it a bit in an airy-fairy way thinking the text was trying to get us to be philosophical about it. Finally I looked at my teacher's guide.
4 1/3 = 4.333...
2/3 = 0.666...
therefore 4 1/3 + 2/3= 4.999...
Based on the above working, Weimin is correct.
No, Singapore DM didn't want airy fairy crap from us. It wanted real problem solving. It wanted our brains flexible and engaged in order to determine what it was poor Weimin was getting at. Which is what Singapore texts always want. No art projects, no, "if 5 was a colour what would it be?", no dry, soul sucking repetition. Just honest to goodness mathematical thinking that in turns frustrates the hell out of us and makes us giddy with excitement when we realize what it's trying to tell us.