题目内容
下面各题怎样简便就怎样算.
(1)2.7×99+2.7
(2)
(3)3.93+1.64+6.07+8.36
(4)(7.9-3.06÷0.51)×5
(5)15-11.17-2.83
(6)15×(
+
)
解:(1)2.7×99+2.7,
=2.7×(99+1),
=2.7×100,
=270;
(2)
,
=
+
-
,
=
;
(3)3.93+1.64+6.07+8.36,
=(3.93+6.07)+(1.64+8.36),
=10+10,
=20;
(4)(7.9-3.06÷0.51)×5,
=(7.9-6)×5,
=1.9×5,
=9.5;
(5)15-11.17-2.83,
=15-(11.17+2.83),
=15-14,
=1;
(6)15×(
+
),
=15×
+15×
,
=5+3,
=8.
分析:(1)(6)根据乘法分配律简便计算;
(2)先通分,再计算;
(3)先变形为(3.93+6.07)+(1.64+8.36),再计算;
(4)先计算括号里面的,再计算括号外面的乘法;
(5)先变形为15-(11.17+2.83),再计算.
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算.
=2.7×(99+1),
=2.7×100,
=270;
(2)

=



=

(3)3.93+1.64+6.07+8.36,
=(3.93+6.07)+(1.64+8.36),
=10+10,
=20;
(4)(7.9-3.06÷0.51)×5,
=(7.9-6)×5,
=1.9×5,
=9.5;
(5)15-11.17-2.83,
=15-(11.17+2.83),
=15-14,
=1;
(6)15×(


=15×


=5+3,
=8.
分析:(1)(6)根据乘法分配律简便计算;
(2)先通分,再计算;
(3)先变形为(3.93+6.07)+(1.64+8.36),再计算;
(4)先计算括号里面的,再计算括号外面的乘法;
(5)先变形为15-(11.17+2.83),再计算.
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算.

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