×12= | + +1= | × = |
- = | × = | 9× = |
× = | 42× = | 11× = |
× = | = | × = |
×30= | × = | × = |
解: ×12=9, | + +1=1 , | × = , |
- = , | × = , | 9× = , |
× = , | 42× = , | 11× = , |
× = , | = , | × = , |
×30=14, | × = , | × = . |
分析:分数加减法的计算方法:先通分成同分母分数,再分母不变,把分子相加减;
分数乘法的计算方法:分母和分母相乘的积做分母,分子和分子相乘的积做分子,能约分的要先约分再计算.
点评:本题考查了基本的分数乘法的计算,注意能约分的要先约分再乘,结果要化成最简分数.
×12=
+
×
=
-
×
=
=
=
=
×
=
=
=
×30=
×
=
×
=
,
,
,
,
,
,
,
,
,
.