题目内容
(2011?苏州模拟)下面各题,能简便计算的要用简便方法计算.
①(8.5-3)×(0.34÷1.7)
②2.5×(1.9+1.9+1.9+1.9)
③
×
+
÷13
④
÷[1-(
+
)].
①(8.5-3)×(0.34÷1.7)
②2.5×(1.9+1.9+1.9+1.9)
③
7 |
8 |
12 |
13 |
7 |
8 |
④
2 |
15 |
1 |
5 |
1 |
3 |
分析:②可以根据乘法的意义,把加法算式变成乘法,再运用乘法结合律简算;③可以运用乘法分配律简算;其余题目按照先算乘除,再算加减,有括号的先算扩号里面的运算顺序计算.
解答:解:①(8.5-3)×(0.34÷1.7),
=5.5×0.2,
=1.1;
②2.5×(1.9+1.9+1.9+1.9),
=2.5×(4×1.9),
=(2.5×4)×1.9,
=10×1.9,
=19;
③
×
+
÷13,
=
×
+
×
,
=(
+
)×
,
=1×
,
=
;
④
÷[1-(
+
)],
=
÷[1-
],
=
÷
,
=
×
,
=
.
=5.5×0.2,
=1.1;
②2.5×(1.9+1.9+1.9+1.9),
=2.5×(4×1.9),
=(2.5×4)×1.9,
=10×1.9,
=19;
③
7 |
8 |
12 |
13 |
7 |
8 |
=
7 |
8 |
12 |
13 |
7 |
8 |
1 |
13 |
=(
12 |
13 |
1 |
13 |
7 |
8 |
=1×
7 |
8 |
=
7 |
8 |
④
2 |
15 |
1 |
5 |
1 |
3 |
=
2 |
15 |
8 |
15 |
=
2 |
15 |
7 |
15 |
=
2 |
15 |
15 |
7 |
=
2 |
7 |
点评:运算定律是常用的简便运算的方法,要熟练掌握,灵活运用.
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