Question

用简便方法计算下面各题．（1）2.9×0.45+0.29×4.2+0.029×13（2

Answer 1

2.9×0.45+0.29×4.2+0.029×13。这个数可以拔2.9和0.29和0.029。同时变成同一个数，也就是说把0.29变成2.9× 0.42 0.029变成2.9乘以0.13。这样计算起来就比较简便，应用乘法的分配率。

Answer 2

（1）2.9×0.45+0.29×4.2+0.029×13，
=2.9×0.45+2.9×0.42+2.9×0.13，
=2.9×（0.45+0.42+0.13），
=2.9×1，
=2.9；

（2）3.84×9.6+0.96×61.6，
=3.84×9.6+9.6×6.16，
=（3.84+6.16）×9.6，
=10×9.6，
=96．

Answer 3

2.9×0.45+0.29×4.2+0.029×13
=2.9×0.45+2.9×0.1×4.2+2.9×0.01×13
=2.9×（0.45+0.42+0.13）
=2.9×1
=2.9