邏輯推演沙盤撥算 (2)
歸零即開始,握筆撥珠報數寫答,
十進制即 『 滿十 』進位的數制,
每個位數都有 0～９共十個數碼,
加法減法計算要領『只有 補十』
1 + 9 = 10 , 2 + 8 = 10 , 3 + 7 = 10
4 + 6 = 10 , 5 + 5 = 10 ,,,
+1 = +10 -9 , +2 = +10 -8
+3 = +10 -7 , +4 = +10 -6
+5 = +10 -5 , +6 = +10 -4
+7 = +10 -3 , +8 = +10 -2
+9 = +10 -1 ,,,
-1 = + 9 -10 , -2 = + 8 -10
-3 = + 7 -10 , -4 = + 6 -10
-5 = + 5 -10 , -6 = + 4 -10
-7 = + 3 -10 , -8 = + 2 -10
-9 = + 1 -10 ,,,
『補十』(1,9),(2,8),(3,7),(4,6),(5,5)
所有位數加減“進位退位”準則相同
運用易算盤很容易就理解了“補十”
學習同時『教家人』作對打“競算”
達成『教學相長』自動自發“情境”
易算盤的“學習使用”是『無國界』
“手腦並用終身受益” “最棒的教具”
