| 脱式计算. 1 × +×6 | 6.5× +0.24×4.5-6÷25 |
1 +2 +3 +4 | 12 ÷ -[6 +3 ×(3 -2 )] |
61 × +71 × +81 × | 7 ×0.6+ ×7 )÷ ÷ . |
×
+
×6
=(1
+6
)×
,=8×
,=6;
(2)6.5×
+0.24×4.5-6÷25=6.5×0.24+0.24×4.5-0.24,
=(6.5+4.5-1)×0.24,
=10×0.24,
=2.4;
(3)1
+2
+3
+4
=(1+2+3+4)+(
+
+
+
+),=10+(1-
+
-
+
-
+
-
)÷2,=10+
÷2,=10+
,=10
;(4)12
÷
-[6
+3
×(3
-2
)]=
×
-[6
+
×
],=14-[6
+1
],=14-8,
=6;
(5)61
×
+71
×
+81
×
=
×
+
×
+
×
,=51+61+71,
=183;
(6)(7
×0.6+
×7
)÷
÷
.=(7
×
+
×7
)×
×
,=(7
+7
)×
×
×
,=15×
×
×
,=35.
分析:算式(1)(2)(6)可根据乘法分配律计算;
算式(3)可根据分数巧算公式:
=(
-
)÷2进行计算;算式(4)(5)根据四则混合运算的运算顺序计算即可:先算乘除,再算加减,有括号的要先算括号里面的.
点评:完成本题要认真分析式中数据的特点及内在联系,然后运用合适的方法进行计算.