考點(diǎn):整數(shù)、分?jǐn)?shù)、小數(shù)、百分?jǐn)?shù)四則混合運(yùn)算,運(yùn)算定律與簡(jiǎn)便運(yùn)算
專(zhuān)題:運(yùn)算順序及法則,運(yùn)算定律及簡(jiǎn)算
分析:(1)按照先同時(shí)算括號(hào)里面的,再算乘法計(jì)算方法解答,
(2)(5)(7)運(yùn)用乘法分配律解答,
(3)按照先算小括號(hào)里面的,再算中括號(hào)里面的,最后算括號(hào)外面的順序計(jì)算解答,
(4)按照先同時(shí)算乘法和除法,再算加法順序計(jì)算解答,
(6)運(yùn)用減法性質(zhì)解答.
解答:
解:(1)(
-
)×(
+
)
=
×
=
;
(2)
÷7+
×
=
×(
+
)
=
×
=
;
(3)[1-(
+
)]÷
=[1-
]÷
=
÷
=1
;
(4)
÷
+
×
=
+
=1
;
(5)(
+
-
)×12
=
×12+
×12-
×12
=2+9-8
=3;
(6)2-
÷
-
=2-(
+
)
=2-2
=0;
(7)99×
=100×
-1×
=99-
=98
.
點(diǎn)評(píng):本題考查知識(shí)點(diǎn):(1)依據(jù)四則運(yùn)算計(jì)算方法正確進(jìn)行計(jì)算,(2)正確運(yùn)用簡(jiǎn)便方法解決問(wèn)題.