=1100-(10+100)*10/21100-10-20-30-...-100用簡便計算 簡算1100-10-20-30...-100,1100-10-20-30-......-100簡便運算公式1100-10-20-30-...-100=1100一(10十90)一(20+80)一(30十70)一(40+60)一50一100=1100一550=550,乘法:減法:=1100-550乘法結合律(a×b)×c=a×(b×c)除法:加法交換律a+b=b+a