1÷ = | 0.4+4.73= | ÷ = | + = |
× = | +0.8= | × ÷ × = | ( + )×120= |
1÷ =50, | 0.4+4.73=5.13, | ÷ = , | + =1, |
× = , | +0.8=1.55, | × ÷ × = , | ( + )×120=70. |
分析:分数乘法:分子相乘的积做分子,分母相乘的积做分母;
分数除法:除以一个数(0除外)等于乘这个数的倒数;
×
÷
×
把除法变成乘法,再运用乘法结合律简算;(
+
)×120运用乘法分配律简算.点评:口算题目,要求快速准确,能用简便方法的要用简便方法.
=
÷
=
=
×
=
+0.8=
,
,
,