解:(1)438+203,
=438+200+3,
=641;
(2)256+199,
=256+200-1,
=455;
(3)416-302,
=416-300-2,
=114;
(4)325-198,
=325-200+2,
=127;
(5)278+498,
=278+500-2,
=776;
(6)3.6+2.7+6.4+7.3,
=(3.6+6.4)+(2.7+7.3),
=10+10,
=20;
(7)
+
+
+
=(
)+(
),
=1+3,
=4;
(8)1.3+4.25+3.7+3,
=(1.3+3.7)+(4.25+3),
=5+7.25,
=12.25;
(9)1874-324-476,
=1874-(324+476),
=1874-800,
=1074;
(10)5-1.4-1.6
=5-(1.4+1.6),
=5-3,
=2;
(11)30-8.12-4.13-7.75
=30-(8.12+4.13+7.75),
=30-20,
=10;
(11)
-
+
=
+
-
,
=1-
,
=
;
(12)4.3-2.45+5.7-6.55
=(4.3+5.7)-(2.45+6.55),
=10-9,
=1;
(13)125×48
=125×8×6,
=1000×6,
=6000;
(14)25×32
=25×4×8,
=100×8,
=800;
(15)35×1.4
=35×0.2×7,
=7×7,
=49;
(16)1.25×88
=1.25×(80+8),
=1.25×80+1.25×8,
=100+10,
=110;
(17)0.25×444
=0.25×4×111,
=111;
(18)32×0.25×12.5
=8×4×0.25×12.5,
=(8×12.5)×(4×0.25),
=100×1,
=100;
(19)25×80×0.04×125
=(125×80)×(25×0.04),
=10000×1,
=10000;
(20)1.9×4×0.5
=1.9×(4×0.5),
=1.9×2,
=3.8
(21)25×1.25×4×0.8
=(25×4)×(1.25×0.8),
=100×1,
=100;
(22)(1.6+1.6+1.6+1.6)×2.5
=1.6×(4×2.5),
=1.6×10,
=16;
(23)(0.7+0.7…+0.7)×12.5(80個0.7相加)
=80×0.7×12.5,
=80×12.5×0.7,
=1000×0.7,
=700;
(24)99×8.6+8.6
=(99+1)×8.6,
=100×8.6,
=860;
(25)99×5.4
=(100-1)×5.4,
=100×5.4-1×5.4,
=540-5.4,
=534.6;
(26)4.8×1.01
=4.8×(1+0.01),
=4.8×1+4.8×0.01,
=4.8+0.048,
=4.848;
(27)95×101-95
=95×(101-1),
=95×100,
=9500;
(28)95×102-190
=95×(100+2)-190,
=95×100+95×2-190,
=9500+190-190,
=9500;
(29)95.6×18+0.4×18
=18×(95.6+0.4),
=18×96,
=18×(100-4),
=18×100-18×4,
=1800-72,
=1728;
(30)(
-
+
)×12
=
×12
×12×
,
=4-2+3,
=5;
(31)(
+
-
)÷
=
×24
×24
×24,
=8+3-1,
=10;
(32)24×(
+
-
)
=
×24
×24
×24,
=8+3-1,
=10;
(33)24÷(
+
-
)
=24
,
=24×
,
=57.;
(34)1.25×3.6+1.25×
+
=1.25×(3.6+3.4+1),
=1.25×8,
=10;
(35)3.3×
+0.75×
+75%
=0.75×(3.3+5.7+1),
=0.75×10,
=7.5;
(36)
×6.6+7.5×
=6.6×(2.5+7.5),
=6.6×10,
=66;
(37)9.56×180-95.6×8
=9.56×180-9.56×80,
=9.56×(180-80),
=9.56×100,
=956;
(38)4.8×37+48×6.3
=48×3.7+48×6.3,
=48×(3.7+6.3),
=48×10,
=480;
(39)9.5×8.8+0.12×95
=(8.8+1.2)×9.5,
=10×9.5,
=950;
(40)
×21
=
×(20+1),
=
×20+
×1,
=19
;
(41)
×33
=
×(30+3),
=
×30+
×3,
=7+
,
=7
;
(42)
÷
,
=
=
;
(43)
÷
=
×48,
=
;
(44)
÷42,
=
×
,
=
;
(45)6×0.75+5×
-3÷4
=(6+5-1)×0.75,
=10×0.75,
=7.5;
(46)5.4÷1.2÷5
=5.4÷(1.2×5),
=5.4÷6,
=0.9;
(47)270÷18,
=15;
(48)120÷(1.2×4)
=120÷1.2÷4,
=100÷4,
=25;
(49)73÷0.8÷12.5
=73÷(0.8×12.5),
=73÷10,
=7.3;
(50)16÷2.5
=16÷(2.5×4)×4,
=16÷10×4,
=6.4;
(51)48÷1.25
=48÷(1.25×8)×8,
=48÷10×8,
=38.4;
(52)
-(
-
)+
=
-
+
+
,
=
;
(53)84-(54-16)
=84-54+16,
=46;
(54)84-(54+16)
=84-70,
=14;
(55)9999×7778+3333×6666
=9999×7778+3333×3×2222,
=9999×7778+9999×2222,
=9999×(7778+2222),
=9999×10000,
=99990000;
(56)3.6×31.4+43.9×6.4
=3.6×(43.9-12.5)+43.9×6.4,
=439-3.6×12.5,
=439-45,
=394;
(57)(
+
)×
=
×
+
×
,
=
+2,
=5
;
(58)
×
+
÷
=(
)×
,
=
;
(59)
-
-
=
-(
+
),
=
-1,
=
;
(60)
×
-
×
=
×(
),
=
×
,
=
;
(61)
×
÷
×
=
÷
×
,
=
;
(62)
-
×
-
=
-
,
=
-(
),
=
-1,
=
;
(63)
×[
÷(
+
)]
=
×[
×
+
×7],
=
×(
+3),
=
×
×3,
=
,
=
;
(64)(0.9+5)×3+2.3
=5.9×3+2.3,
=17.7+2.3,
=20;
(65)56×
=
;
(66)
+
÷
+
=
+
,
=1
;
(67)(
+
)÷(
+
)
=1÷1,
=1;
(68)
÷(
-
)
=
×
,
=
;
(69)(
-
)÷
=
×
-
×
,
=
-
,
=
;
(70)7.2÷(5-0.75-0.25)
=7.2÷[5-(0.75+0.25)],
=7.2÷(5-1),
=7.2÷4,
=1.8;
(71)6.4+3.6÷0.5+4.5
=6.4+7.2+4.5,
=18.1;
(72)(6.4+3.6)÷0.5+4.5
=10÷0.5+4.5,
=20+4.5,
=24.5;
(73)495÷55+495÷45
=9+11,
=20;
(74)8÷0.4+8÷1.6
=20+5,
=25;
(75)0.9+99×0.9
=0.9×(1+99),
=0.9×100,
=90;
(76)5.28-(1.62+2.28)
=5.28-2.28-1.62,
=3-1.62,
=1.38;
(77)
-
+
=0+
,
=
;
(78)4×(
+
)
=4×
+4×
,
=
,
=
;
(79)
+
+
+
=(
)+(
),
=1+1,
=2;
| | | |
(80)2-(+)- =2-, =2-(), =2-1, =1; (81)×+× =()×, =1×, =; (82)×+× =()×, =1×, =; (83)×9+ =(9+1)×, =; (84)(20+)× =20×+×, =14+, =14; (85)(5+)× =5×+×, =4+, =4; (86)(+)×24 =×24+×24, =4+3, =7; (87)×39× =3×, =; | | | |
(88)
×(
+
)
=
×
×
,
=1+
,
=1
;
(89)(
-
)×12
=
×12
×12,
=3-2,
=1;
(90)
×(26×
)
=
×
×26,
=6;
(91)
+
+
+
=(
)+(
),
=1+1,
=2;
(92)17×
-
=(17-1)×
,
=16×
,
=6;
(93)(
+
)×
=
×
×
,
=1+
,
=
;
(94)(
+
)÷
=
×
+
×
,
=
+1,
=1
;
(95)(
+
)÷3
=
×
×
,
=
,
=
;
(96)(
-
)÷
=
×9-
×9,
=
,
=
;
(97)
÷
+
÷
=(
)×
,
=
;
(98)
×(10+
)
=
×10+
×
,
=8
,
=8
;
(99)(21+
)÷
=21×
+
×
,
=15+
,
=15
;
(100)
×
+
×
=(
)×
,
=1×
,
=
;
(101)
÷
+
÷
=(
)×
,
=4×
,
=17;
(102)(
-
)÷
=
×
-
,
=
,
=
;
(103)
×
+
=
,
=
;
(104)
-
×
-
=
-
,
=
-(
),
=
-1,
=
;
(105)
-(
÷
+
)
=
-
-
,
=1-
,
=
;
(106)
+
×
+
=
+(
),
=
+1,
=1
;
(107)1-
÷
-
=1-(
),
=1-1,
=0;
(108)
×
+
÷4
=(
)×
,
=1×
,
=
;
(109)5-(4+
)
=5-4-
,
=1-
,
=
;
(110)1125-997
=1125-1000+3,
=125+3,
=128;
(111)7.46-0.83-2.17
=7.46-(0.83+2.17),
=7.46-3,
=4.46;
(112)12.85-1.17-8.83+1.15
=(12.85+1.15)-(1.17+8.83),
=14-10,
=4;
(113)4.5×102
=4.5×(100+2),
=4.5×100+4.5×2,
=450+9,
=459;
(114)0.4×6.3×25
=0.4×25×6.3,
=10×6.3,
=63;
(115)(4.9+4.9+…+4.9)×2.5(16個4.9相加)
=4.9×16×2.5,
=4.9×(4×2.5×4),
=4.9×40,
=196;
(116)7.5×199
=7.5×(200-1),
=7.5×200-7.5×1,
=1500-7.5,
=1492.5;
(117)(
+
)×36
=
×36,
=4+3,
=7;
(118)1.2×5.7-1.2+5.3×1.2
=(5.7+5.3-1)×1.2,
=10×1.2,
=12;
(119)0.825×102-82.5
=0.825×102-0.825×100,
=0.825×(102-100),
=0.825×2,
=1.65;
(120)46×
=
;
(121)560÷16÷5
=560÷(16×5),
=560÷80,
=7;
(122)3÷2.5,
=1.2;
(123)84+(54-16)
=84+38,
=122;
(124)
+
+
+
=(
+
)+(
+
),
=1+1,
=2;
(125)
-(
÷
+
)
=
-
-
,
=1-
,
=
;
(126)3×(
+
)+
=3×
,
=(
)
,
=1+
,
=1
;
(127)7.2÷(5-0.75+0.25)
=7.2÷4.5,
=1.6;
(128)725÷25+275÷25
=(725+275)÷25,
=1000÷25,
=40;
(129)
×
×
=
×
×
,
=
,
=
;
(130)
×45-
÷
=
×45-
×45,
=0;
(131)48×(
-
)
=48×
,
=40-18,
=22;
(132)
×
+
×
=
,
=
;
(133)(32+
)÷4
=32×
,
=8+
,
=8
;
(134)
÷
÷
=
,
=1;
(135)46×
,
=(45+1)×
,
=45×
+
;
=2
;
(136)
×
+
÷9
=(
)×
,
=1×
,
=
.
分析:本題按照先算乘除再算加減,有括號的先算括號里面的順序運(yùn)算.注意觀察算式的特點(diǎn),能運(yùn)用運(yùn)算定律簡算,或者其它簡便方法簡算的要簡算.
點(diǎn)評:本題是考察的基本運(yùn)算法則,根據(jù)運(yùn)算順序計算.本題有很多可以簡算,用相關(guān)的運(yùn)算定律簡算.