解:(1)
×
+
÷
,
=
×
+
×
,
=
×(
+
),
=
×1,
=
;
(2)[
-(
-
)]×
,
=[
-
]×
,
=
×
,
=
;
(3)9999+9998+9997+9996,
=(10000-1)+(10000-2)+(10000-3)+(10000-4),
=40000-10,
=39990;
(4)812-700÷(9+31×11),
=812-700÷(9+341),
=812-700÷350,
=812-2,
=810;
(5)1.25×3.6×8×2.5-12.5×2.4,
=1.25×3.6×8×2.5-1.25×24,
=1.25×(3.6×8×2.5-24),
=1.25×[3.6×2×(4×2.5)-24],
=1.25×[7.2×10-24],
=1.25×48,
=1.25×8×6,
=10×6,
=60;
(6)
+7.4-
+3.6,
=(
-
)+(7.4+3.6),
=
+11,
=11
.
分析:(1)把除法改為乘法,運(yùn)用乘法分配律簡(jiǎn)算;
(2)先算小括號(hào)內(nèi)的,再算中括號(hào)內(nèi)的,最后算括號(hào)外的;
(3)把原式變?yōu)椋?0000-1)+(10000-2)+(10000-3)+(10000-4),運(yùn)用加法結(jié)合律簡(jiǎn)算;
(4)先算括號(hào)內(nèi)的乘法,再算括號(hào)內(nèi)的加法,然后算括號(hào)外的除法,最后算減法;
(5)把原式變?yōu)?.25×3.6×8×2.5-1.25×24,運(yùn)用乘法分配律簡(jiǎn)算;
(6)運(yùn)用加法交換律與結(jié)合律簡(jiǎn)算.
點(diǎn)評(píng):此題考查了四則混合運(yùn)算,注意運(yùn)算順序和運(yùn)算法則,靈活運(yùn)用所學(xué)的運(yùn)算定律進(jìn)行簡(jiǎn)便計(jì)算.