(1/3+1/5)×15 =1/3×15+1/5×15 =5+3 =8 (1/9+1/3)×27 =1/9×27+1/3×27 =3+9 =12 (1/6+1/4)×36 =1/6×36+1/4×36 =6+9 =15 89×7/88 =(88+1)×7/88 =7+7/88 =7又7/88
①12.5×8.88=12.5×（1.11×8）=（12.5×8）×1.11=100×1.11=111②1.9+19.9+199.9+0.3=1.9+19.9+199.9+0.1+0.1+0.1=（1.9+0.1）+（19.9+0.1）+（199.9+0.1）=2+20+200=222③10.01×101-10.01=10.01×（101-1）=10.01×100=1001
17乘9分之5乘34分之1乘9分之1 简便算法 =（17x1/34）x（5/9x1/9） =1/2x5/81 =5/162
1÷1=1 2÷1=2 2÷2=1 4÷2=2 3÷1=3 3÷3=1 6÷3=2 9÷3=3 4÷1=4 4÷4=1 8÷4=2 12÷4=3 16÷4=4 5÷1=5 5÷5=...
4.8×5.6+5.6×6.2-5.6 =5.6x(4.8+6.2-1) =5.6x10 =56
9/13×8-9/13 =9/13x(8-1) =9/13x7 =63/13 =4又13分之11
12×101－12＋300 =12x（101-1）+300 =12x100+300 =1200+300 =1500
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