考點(diǎn):分?jǐn)?shù)的四則混合運(yùn)算,分?jǐn)?shù)的簡便計(jì)算
專題:運(yùn)算順序及法則,運(yùn)算定律及簡算
分析:(1)把除法化成乘法,再運(yùn)用乘法的分配律進(jìn)行簡算;
(2)先分別求出乘除法算式的結(jié)果,再算減法;
(3)運(yùn)用乘法的分配律進(jìn)行簡算;
(4)先運(yùn)用乘法的分配律進(jìn)行簡算,再運(yùn)用加法的結(jié)合律進(jìn)行簡算;
(5)運(yùn)用乘法的分配律進(jìn)行簡算;
(6)先算小括號(hào)里的加法,再算中括號(hào)里的乘法,最后算括號(hào)外的除法.
解答:
解:(1)
×
+
÷31
=
×
+
×
=(
+
)×
=1×
=
;
(2)
÷
-
×
=
-
=
;
(3)(
+
-
)×12
=
×12+
×12-
×12
=4+3-2
=7-2
=5;
(4)(
+
)×8+
=
×8+
×8+
=3+
+
=3+(
+
)
=3+1
=4;
(5)12×(
-
)×11
=12×
×11-12×
×11
=48-11
=37;
(6)
÷[(
+
)×
]
=
÷[
×
]
=
÷
=
.
點(diǎn)評(píng):四則運(yùn)算,先弄清運(yùn)算順序,然后再進(jìn)一步計(jì)算即可,能簡算的要簡算.