题目内容
①139×![]() ![]() | ②73×![]() |
![]() ![]() ![]() | ④88.76×4-8.76÷0.25 |
⑤![]() ![]() ![]() | ⑥4.6×![]() ![]() ![]() |
解:①139×
-137×
,
=(139-1)×
,
=138×
,
=137;
②73×
,
=(75-2)×
,
=75×
-2×
,
=74-1
,
=72
;
③
×(15×
)×
,
=(
)×(15×
),
=
2,
=
;
④88.76×4-8.76÷0.25,
=88.76×4-8.76×4,
=(88.76-8.76)×4,
=80×4,
=320;
⑤
÷(
×
),
=
,
=
,
=1
;
⑥4.6×
+8.4÷
-
×5,
=4.6×
+8.4×
5,
=(4.6+8.4-5)×
,
=8×
,
=11.
分析:①139×
-137×
,将原式转化为:(139-1)×
,再运用乘法分配律进行简算;
②73×
,转化为:(75-2)×
,运用乘法分配律进行简算;
③
×(15×
)×
,运用乘法交换律和结合律进行简算;
④88.76×4-8.76÷0.25,把0.25化成分数是
,再把除数转化为乘它的倒数,运用乘法分配律进行简算;
⑤
÷(
×
),根据除法的运算性质,转化为:
,把除数转化为乘它的倒数进行简算;
⑥4.6×
+8.4÷
-
×5,首先把除数转化为乘它的倒数,再运用乘法分配律进行简算.
点评:除以主要考查分数、小数四则混合运算,要求学生牢固掌握运算顺序和它们的计算法则,并且能够灵活选择简便方法进行简算.


=(139-1)×

=138×

=137;
②73×

=(75-2)×

=75×


=74-1

=72

③



=(


=

=

④88.76×4-8.76÷0.25,
=88.76×4-8.76×4,
=(88.76-8.76)×4,
=80×4,
=320;
⑤



=

=

=1

⑥4.6×



=4.6×



=(4.6+8.4-5)×

=8×

=11.
分析:①139×



②73×


③



④88.76×4-8.76÷0.25,把0.25化成分数是

⑤




⑥4.6×



点评:除以主要考查分数、小数四则混合运算,要求学生牢固掌握运算顺序和它们的计算法则,并且能够灵活选择简便方法进行简算.

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