(1)1125-997(8)998+1246(16)4數(shù)學(xué)公式+3.2+5數(shù)學(xué)公式+6.8
(2)12數(shù)學(xué)公式-(1數(shù)學(xué)公式+2數(shù)學(xué)公式(9)400÷125÷8(17)25×(37×8)
(3)(數(shù)學(xué)公式-數(shù)學(xué)公式)×12(10)1數(shù)學(xué)公式×2數(shù)學(xué)公式×數(shù)學(xué)公式
(11)34×(2+數(shù)學(xué)公式
(18)125×8.8
(4)4.35+4.25+3.65+3.75(12)3.4×99+3.4(19)17.15-8.47-1.53
(5)17數(shù)學(xué)公式-3數(shù)學(xué)公式-4數(shù)學(xué)公式(13)數(shù)學(xué)公式÷2數(shù)學(xué)公式+數(shù)學(xué)公式×數(shù)學(xué)公式(20)0.125×0.25×32
(6)22.3-2.45-5.3-4.55(14)(數(shù)學(xué)公式+數(shù)學(xué)公式+數(shù)學(xué)公式)×72(21)4.25-3數(shù)學(xué)公式-(2數(shù)學(xué)公式-1數(shù)學(xué)公式
(7)187.7×11-187.7(15)43數(shù)學(xué)公式×數(shù)學(xué)公式+57.125×數(shù)學(xué)公式-0.5(22)2.42÷數(shù)學(xué)公式+4.58×數(shù)學(xué)公式-4÷3.

解:(1)1125-997
=1125-(997+3)+3
=1125-1000+3
=128;
(2)12-(1+2
=--
=;
(3)(-)×12
=×12-×12
=4-2
=2;
(4)4.35+4.25+3.65+3.75
=(4.35+3.65)+(4.25+3.75)
=8+8
=16;
(5)17-3-4
=--
=;
(6)22.3-2.45-5.3-4.55
=22.3-5.3-(2.45+4,55)
=17-7
=10;
(7)187.7×11-187.7
=118.7×(11-1)
=118.7×10
=1187;
(8)998+1246
=(998+2)+1246-2
=1000+1246-2
=2244;
(9)400÷125÷8
=400÷(125×8)
=400÷1000
=0.4;
(10)1×2×
=××
=;
(11)34×(2+
=34×2+34×
=68+13
=81;
(12)3.4×99+3.4
=3.4×(99+1)
=3.4×100
=340;
(13)÷2+×
=(+)×
=1×
=;
(14)(++)×72
=×72+×72+×72
=66+28+15
=109;
(15)43×+57.125×-0.5
=(43.875+57.125)×0.5-0.5
=101×0.5-0.5
=50.5-0.5
=50;
(16)4+3.2+5+6.8
=(+)+(3.2+6.8)
=10+10
=20;
(17)25×(37×8)
=25×8×37
=200×37
=7400;
(18)125×8.8
=125×8+125×0.8
=1000+100
=1100;
(19)17.15-8.47-1.53
=17.15-(8.47+1.53)
=17.15-10
=7.15;
(20)0.125×0.25×32
=(0.125×8)×(0.25×4)
=1×1
=1;
(21)4.25-3-(2-1
=(4.25+)-(+
=6-6
=0;
(22)2.42÷+4.58×-4÷3
=(2.42+4.58-1)×
=6×
=8;
分析:根據(jù)加法和乘法的運算定律,減法、除法的運算性質(zhì),及加減法的速算方法進(jìn)行計算.
點評:此題主要考查,利用運算定律、運算性質(zhì)進(jìn)行小數(shù)、分?jǐn)?shù)四則混合運算的簡便計算.
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