小数四则混合运算和简便运算(2) 1. 5 10 0.49 3.63 11.3 0.36 2.(1)A (2)C 3. 2×(7.5 - 5.7)+4.8 4.38÷2.5÷4 = 2×1.8+4.8 = 4.38÷(2.5×4) = 3.6+4.8 = 4.38÷10 = 8.4 = 0.438 6.3×2.1+7.9×6.3 73.8 - 0.15×5 - 0.25 = 6.3×(2.1+7.9) = 73.8 - 0.75 - 0.25 = 6.3×10 = 73.8 -(0.75+0.25) = 63 = 73.8 - 1 = 72.8 8.52 - 3.45+2.55 28.6×101 - 28.6 = 8.52 -(3.45 - 2.55) = 28.6×(101 - 1) = 8.52 - 0.9 = 28.6×100 = 7.62 = 2860 4.(121-3.8×5)÷(3.8+4.7)=1 |