解:
(1)14.76-5.76-
,
=9-
,
=8
;
(2)4
÷8
×2
,
=
×
×
,
=
;
(3)64
×
,
=
×
,
=
;
(4)6
×5-3
×2,
=(6+
)×5-(3+
)×2,
=(6×5+
×5)-(3×2+
×2),
=30+
-6-
,
=(30-6)+(
-
),
=24+
,
=26
;
(5)13×
+4
×10,
=5
+46,
=51
;
(6)198÷198
+
,
=198×
+
,
=
+
,
=1;
(7)12.5×
+3
×1.25,
=1.25×10×
+3
×1.25,
=1.25×
+3
×1.25,
=1.25×(
+3
),
=1.25×5,
=6.25;
(8)
+
+
+
,
=
+
+
+
,
=1-
+
-
+
-
+
-
,
=1-
,
=
;
(9)(3.7×5
-4.7×3.7)÷
,
=3.7×(5
-4.7)÷
,
=3.7×1÷
,
=3.7÷
,
=11.1;
(10)[0.3+(
+□)×3]÷0.3=860,
[0.3+(
+□)×3]÷0.3=860,
[0.3+1.5+□×3]÷0.3=860,
[1.8+□×3]÷0.3=860,
6+10×□=860,
10×□=854,
□=85.4;
(11)56×
,
=(55+1)×
,
=55×
+1×
,
=54+
,
=54
,
(12)18.75-(4.5-7.25),
=18.75-4.5+7.25,
=(18.75+7.25)-4.5,
=26-4.5,
=21.5;
(13)3.6×31
+3.14×64,
=3.6×31.4+3.14×64,
=3.6×31.4+31.4×6.4,
=(3.6+6.4)×31.4,
=10×31.4,
=314;
(14)132
÷131,
=(131+1
)×
,
=131×
+1
×
,
=1+
×
,
=1+
,
=1
;
(15)3×
+4×
+5×
+6×
,
=(3×
+5×
)+(4×
+6×
),
=
+
,
=2+6,
=8;
(16)112×(24-4
)÷2.4,
=112×(24-4.8)×
,
=112×(24×
-4.8×
),
=112×(10-2),
=112×8,
=896;
(17)(81.4+
+
+
)÷(
+
+
),
=(81.4+
)÷
,
=(81.4+
)×
,
=81.4×
+
×
,
=132+1,
=133;
(18)41.2×8.1+11×9
+53.7×1.9,
=41.2×8.1+11×9.25+(41.2+12.5)×1.9,
=41.2×8.1+11×9.25+41.2×1.9+12.5×1.9,
=(41.2×8.1+41.2×1.9)+11×9.25+12.5×1.9,
=41.2×(8.1+1.9)+11×(8+1.25)+12.5×1.9,
=41.2×10+11×8+11×1.25+1.25×19;
=412+88+1.25×(11+19),
=500+1.25×30,
=500+37.5,
=537.5;
(19)
+
+
+
+
+
+
,
=
+
+
+
+
+
+
,
=1-
+
-
+
-
+
-
+
-
+
-
+
-
,
=1-
,
=
;
(20)
+
+
+…+
,
=
×(1-
+
-
+
-
+…+
-
),
=
×(1-
),
=
×
,
=
.
分析:(1)按照從左向右的順序進(jìn)行計(jì)算;
(2)按照從左向右的順序進(jìn)行計(jì)算;
(3)把帶分?jǐn)?shù)化成假分?jǐn)?shù),再約分計(jì)算;
(4)根據(jù)乘法分配律進(jìn)行計(jì)算;
(5)先算乘法,再算減法;
(6)先算乘法,再算加法;
(7)根據(jù)乘法分配律進(jìn)行計(jì)算;
(8)根據(jù)分?jǐn)?shù)的拆項(xiàng)進(jìn)行計(jì)算;
(9)小括號(hào)里面的根據(jù)乘法分配律進(jìn)行計(jì)算,再算除法;
(10)把□看作未知數(shù),根據(jù)等式的性質(zhì)進(jìn)行解方程即可;
(11)根據(jù)乘法分配律進(jìn)行計(jì)算;
(12)去掉括號(hào),再根據(jù)加法交換律進(jìn)行計(jì)算;
(13)根據(jù)乘法分配律進(jìn)行計(jì)算;
(14)根據(jù)乘法分配律進(jìn)行計(jì)算;
(15)根據(jù)加法交換律和結(jié)合律進(jìn)行計(jì)算;
(16)根據(jù)乘法分配律進(jìn)行計(jì)算;
(17)先算小括號(hào)里面的加法,根據(jù)乘法分配律進(jìn)行計(jì)算;
(18)根據(jù)乘法分配律進(jìn)行計(jì)算;
(19)根據(jù)分?jǐn)?shù)的拆項(xiàng)進(jìn)行計(jì)算;
(20)根據(jù)分?jǐn)?shù)的拆項(xiàng)進(jìn)行計(jì)算.
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,能簡(jiǎn)算的要簡(jiǎn)算.