回複:My daughter's 3rd grade math. Need help...
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綠蘋果園
於
2010-01-17 23:58:46
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Why 3rd grade math? Maybe because the "only" operator needed here is addition:
1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
5 10 10 5
15 20 15
35 35
70