Question

请教~五年级上册数学简便运算题！！！急！！！

最好是递等式计算谢谢！！

1）3.7×1.4×0.05

2）2.7×3.7+0.37×73

3）2.3×6.7-9.24

4）1.25×23×1.6

5）16.5×9.9

6）0.64+0.36×0.25

7）3.9×7.8+39×0.12+3.9

8）3.05-2.05×1.4

Answer 1

1）3.7×1.4×0.05
=3.7×0.07
=0.259

2）2.7×3.7+0.37×73
=3.7×（2.7+7.3）
=3.7×10
=37

3）2.3×6.7-9.24
=15.41-9.24
=6.17

4）1.25×23×1.6
=1.25×8×2.3×2
=10×4.6
=46

5）16.5×9.9
=16.5×（10-0.1）
=165-1.65
=163.35

6）0.64+0.36×0.25
=0.64+0.09
=0.73

7）3.9×7.8+39×0.12+3.9
=3.9×（7.8+1.2+1）
=3.9×10
=39

8）3.05-2.05×1.4
=1+2.05-2.05×1.4
=1-2.05×0.4
=1-0.82
=0.18

Answer 2

1）3.7×1.4×0.05
=3.7×0.07
=0.259

2）2.7×3.7+0.37×73
=3.7×（2.7+7.3）
=3.7×10
=37

3）2.3×6.7-9.24
=15.41-9.24
=6.17

4）1.25×23×1.6
=1.25×8×2.3×2
=10×4.6
=46

5）16.5×9.9
=16.5×（10-0.1）
=165-1.65
=163.35

6）0.64+0.36×0.25
=0.64+0.09
=0.73

7）3.9×7.8+39×0.12+3.9
=3.9×（7.8+1.2+1）
=3.9×10
=39

8）3.05-2.05×1.4
=1+2.05-2.05×1.4
=1-2.05×0.4
=1-0.82
=0.18

Answer 3

1） 3.7×1.4×0.05
=3.7 x (1.4x0.05)
=3.7x0.07=0.259

2） 2.7×3.7+0.37×73
=37(2.7x0.1+73x0.01)
=37x(0.27+0.73)=37

3） 2.3×6.7-9.24
=15.41-9.24=6.17

4） 1.25×23×1.6
=0.25x5x23x1.6
=0.25x4x0.4x5x23
=1x2x23=46

5） 16.5×9.9
=16.5x(10-0.1)
=165-1.65=163.35

6） 0.64+0.36×0.25
=0.64+0.6x0.6x0.5x0.5
=0.64+0.3x0.3
=0.64+0.09
=0.73

7） 3.9×7.8+39×0.12+3.9
=39x(0.1x7.8+0.12+0.1)
=39

8） 3.05-2.05×1.4
=2.05+1-2.05x1.4
=2.05(1-1.4)+1
=2.05x(-0.4)+1
=1-0.82
=0.18