101×9.9 =(100+1)×9.9 =100×9.9+9.9 =990+9.9 =999.9 1.95+2.17+7.05 =2.17+(1.95+7.05) =2.17+9 =11.17 5.8+3.55+1.45+ 2.2 =(5.8+2.2)+(3.55+1.45) = 8+5 =13 6.88 - 3.4 - 1.6 =6.88-(3.4+1.6) =6.88-5 =1.88 65.4×38+63×65.4-65.4 =65.4×(38+63-1) =65.4×100 =6540 2.41+9.6+5.59+0.4 =(2.41+5.59)+(9.6+10.4) =8+10 =18 8.28+5.21 -6.28 =8.28-6.28+5.21 =2+5.21 =7.21 0.39 + 0.87 + 8.61 =(0.39+ 8.61)+ 0.87 =9+0.87 =9.87