小學(xué)奧數(shù)：計(jì)算專題《小數(shù)的巧算》練習(xí)題

1、小學(xué)奧數(shù)：計(jì)算專題?小數(shù)的巧算?練習(xí)題選擇題共7小題計(jì)算：2.3+0.08+ 1.25=(2.C. 2.3D. 0.23卜面有四個(gè)算式: 0.6+ 0. 133= 0. 7330.625 = 3 $+色=-=旦=!(!8 14 214+2 163,19X 4=14其中正確的算式是3.4.C.B.和C.和D.和0.456X2.1的結(jié)果相同的算式是4.56 X 21B. 21 X 0.0456C.45.6X0.21D. 456X 0.02161.2+3.4計(jì)算結(jié)果相同的是6.12+0.340.612X 0.034B.D.612 + 0.34612+345.計(jì)算(1.25X 7+0.25+3) +

2、2+0.36X 3 =6.A . 19.48B . 20.08C.20.12D. 21.02如果 3.2+av 3.2,那么 a ()A.等于1B.大于0而小于D.C.小于17.卜列算式中,積最小的是A . 555.5 X 55.55B.555.5 X 555.5C. 555X 555D.55.55 X 55.55二.填空題共15小題8.算式20.17- 12.02 + 6) X 6的計(jì)算結(jié)果是9.計(jì)算:53.3+ 0.23+ 0.91 X 16.1 + 0.82 =10.計(jì)算39.07- 22.78-3.4 =11.計(jì)算0.1+0.2+0.3-+0.8+0.9+1 =12.計(jì)算13.計(jì)算:3

3、.85X 2.6+1.5X 0.26- 0.125 X 16X 0.5 =96.75 X 9+64.5 X 31+32.25 X 11 =14 .計(jì)算：1.25X6.21X16+5.8=.15 .計(jì)算：101.8- (43.811) =.16 .計(jì)算：0.5+1.1+0.8 = (結(jié)果寫成小數(shù)形式)17 .計(jì)算：91.5+19.8+80.2 =.18 .計(jì)算：2.4 X 2.7+6.3X 2.4+9 X 1.6 =.19 .計(jì)算：64.2X4.12+5.88X28.5+5.88X 35.7 =.20 .計(jì)算：(102.4+89.6 38X5) X ( 2021 126X 16) =.21 ,算

4、式 20.15 + (1.2+1.9) X(4" 32+22T2)的計(jì)算結(jié)果是 .22 .計(jì)算 73.74+2.47+26.26 - 26.36+67.53 - 43.64=.三.計(jì)算題(共15小題)23 . 2.8X27+28X2.9+2.8X4424 .計(jì)算 1.9+19.99 X 2+199.999 X 3+1999.9999 X 4+19999.99999 X 5=.25 .計(jì)算 0.8 + 9+0.1 + 9=; 201.7 X 4.5+2021 X 0.35+20.17 X 20=;(0.1+0.2+0.3+0.4) X ( 1+0.1+0.2+0.3) - ( 1+0.

5、1+0.2+0.3+0.4 ) X ( 0.1+0.2+0.3) =26 .計(jì)算：(20.15+40.3) X 33+20.15.27 .計(jì)算：0.79X 0.46+7.9X 0.24+11.4X 0.079.28 . 26.39X 36+26.39X 83- 26.39X 1929 .計(jì)算:8X 25X 2X 1.25X 0.5X 0.4640X 12.5X 0.25X 0.0530 .計(jì)算：0.875X 0.8+0.75X0.4+0.5 X 0.2.31 . (1) 1.25X 0.32X 2.5(2) 25X4.432 , 465X 8.2+465X29.6 - 365X 37.8.33

6、 .計(jì)算題:0.1+0.2+0.3+0.4+0.9+0.1+0.11+0.12+0.98+0.99T T§；-+：-+ l+y (1+y) X (1+y)(1+y) X (1+y) X X (1+-)34 .計(jì)算：412+0.5+240+ 12.5+0.835 .計(jì)算17.48X37- 174.8X 1.9+1748 X 0.827.816 X 1.45+3.14 X 2.184+1.69 X 7.81636 .計(jì)算(7.2X7.5X 8.1) + ( 1.2X 2.5X 2.7)0.9+9.9+99.9+999.9+9999.937 . 9.8+99.8+999.8+9999.8+

7、10小學(xué)奧數(shù)：計(jì)算專題?小數(shù)的巧算?練習(xí)題參考答案與試題解析選擇題共7小題1 .【解答】解：2.3+0.08+1.25= 2.3 + (0.08X 1.25)=2.3 + 0.1=23應(yīng)選：B.2.【解答】解：0.6+0. 1 33= 0.T33不正確;0.625=2正確; s5,3 3+5+=14 2 14+2-=!不正確;16 23.【解答】解：0.456X2.1= 4.56X 0.21= 0.0456X21= 45.6X 0.021= 456X 0.0021應(yīng)選：B.4 .【解答】解：61.2+3.4=612+34應(yīng)選：D .5 .【解答】解：(1.25X 7+0.25+3) + 2+0

8、.36X3=( 1.25+0.25X 7+3) + 2+1.08,=(5X 7+3) + 2+1.08,=(35+3) + 2+1.08,= 38 + 2+1.08 ,=19+1.08,= 20.08.應(yīng)選：B.6 .【解答】解：由于一個(gè)非零數(shù),除以一個(gè)比1小的數(shù),得到的商比這個(gè)數(shù)大,除以一個(gè)比 1大的數(shù),得到的商比這個(gè)數(shù)小,所以a> 1應(yīng)選：D .7 .【解答】解：555.5 X 55.55 V 555.5 X 555.5,所以舍去 B555.5 X55.55V555X 555,所以舍去 C555.5 X 55.55 > 55.55 X 55.55,所以舍去 A應(yīng)選：D .2 .

9、填空題(共15小題)8 .【解答】解：(20.17 12.02+6) X 6= 20.17X 6- 12.02+6X 6=121.02- 12.02=109故答案為：109.9 .【解答】解：53.3+ 0.23 + 0.91 X 16.1 + 0.82=( 53.3+0.82) X ( 16.1 + 0.23) + 0.91= 65X70+ 0.91=13X5X 10X7+0.7+1.3=10X5X 10X 10= 5000故答案為：5000.10 【解答】解：39.07 22.78+3.4= 39.07- 6.7=32.3711 【解答】解：原式=(0.1 + 1 ) X 10 + 2=1

10、.1 X5= 5.5故填5.512 【解答】解：原式=3.85X 2.6+0.15X 2.6- 0.125X 16X 0.5=( 3.85+0.15) X 2.6- 0.125X 8X 2X 0.5=4X 2.6- 1 X 1=10.4- 1=9.4故填9.413 .【解答】解：96.75X 9+64.5X 31+32.25X 11=32.25X ( 3X9) +32.25 X ( 2X 31) +32.25X 11=32.25 X ( 3X9+2X 31+11)=32.25 X 100= 3225故答案為：32.25.14 .【解答】解：1.25X6.21 X 16+5.8=(1.25X 8

11、) X ( 2X 6.21) +5.8= 10X12.42+5.8=124.2+5.8=130故答案為：13015 .【解答】解：101.8- ( 43.8- 11)=101.8-32.869故答案為：69.16 .【解答】解：0.5+1.1+0.8 =1.6+0.8=2.4故答案為：2.4.17 .【解答】解：91.5+19.8+80.2= 91.5+ (19.8+80.2)= 91.5+100=191.5故答案為：191.5.18 .【解答】解：2.4X 2.7+6.3X 2.4+9 X 1.6= 2.4X (2.7+6.3) +9X 1.6= 2.4X9+9X 1.6=9X (2.4+1

12、.6)= 9X4=36故答案為：3619 .【解答】解：64.2X 4.12+5.88 X 28.5+5.88 X 35.7= 64.2X 4.12+5.88 X ( 28.5+35.7)= 64.2X4.12+5.88X64.2= 64.2X ( 4.12+5.88)= 64.2X 10=642故答案為：642.20 .【解答】解：( 102.4+89.6 -38X 5) X ( 2021- 126X 16)=( 102.4+89.6 - 38X 5) X ( 2021-2021)=(102.4+89.6 38X 5) X 0故答案為：0.21 .【解答】解：20.15+ ( 1.2+1.9

13、) X ( 42- 32+22T2)= 20.15+3.1 X 10= 6.5X10=65;故答案為：65.22 .【解答】解：73.74+2.47+26.26 26.36+67.53 43.64=( 73.74+26.26) + (2.47+67.53) - ( 26.36+43.64)=100+70 - 70=100.故答案為：100.3 .計(jì)算題(共15小題)23 .【解答】解：2.8X 27+28X2.9+2.8X44= 2.8X27+2.8X29+2.8X44= 2.8X (27+29+44)= 2.8X100= 28024 .【解答】解：原式= 2+20 X 2+200 X 3+2

14、000 X 4+20000 X5 ( 0.1+0.01 X 2+0.001 X 3+0.0001 X 4+0.00001 X 5)=108642 - 0.12345=108641.87655故答案為:108641.87655.25 .【解答】解： 0.8+9+0.1+9=(0.8+0.1) +9=0.9 + 9= 0.1 201.7 X 4.5+2021 X 0.35+20.17 X 20=201.7 X 4.5+201.7 X 3.5+201.7 X 2= 201.7X ( 4.5+3.5+2)= 201.7X 10= 2021(0.1+0.2+0.3+0.4) X ( 1+0.1+0.2+

15、0.3) - ( 1+0.1+0.2+0.3+0.4 ) X ( 0.1+0.2+0.3)=1 X 1.6 - 2 X 0.6=1.6 - 1.2=0.426 .【解答】解：(20.15+40.3) X 33+20.15=(20.15+20.15 X 2) X 33+20.15= 20.15X 3X 33+20.15= 20.15X ( 3X33+1)= 20.15X 100= 202127 .【解答】解：0.79X 0.46+7.9 X 0.24+11.4 X 0.079=0.79X 0.46+0.79 X 2.4+1.14X 0.79= 0.79X ( 0.46+1.14+2.4)= 0.

16、79X4=(0.8-0.01) X 4= 0.8X4 - 0.01 X 4=3.2 - 0.04= 3.1628 .【解答】解：26.39 X 36+26.39 X 83 - 26.39 X 19=26.39 X ( 36+83- 19)=26.39 X 100= 263929 .【解答解：8X25X2X 1.25X 0.5X 0.4=(8X 1.25) X ( 25 X 0.4) X ( 2X 0.5)= 10X10X 1=100640X 12.5X 0.25X 0.05= 8X 20X4X 12.5X 0.25X 0.05=( 8X 12.5) X ( 4X 0.25) X ( 0.05X

17、 20)=100X 1 X 1=10030 .【解答】解：0.875X 0.8+0.75X 0.4+0.5X 0.2=X 0.8+Hx 0.4+X 0.2842= 0.7+0.3+0.1=1.131 .【解答】解：(1) 1.25X0.32X 2.5=1.25X 0.8X 0.4X 2.5=(1.25X 0.8) X ( 0.4 X 2.5)= 1X1=1(2) 25X4.4= 25X4X 1.1=100X 1.1= 11032 .【解答】解：465X 8.2+465X29.6 365X 37.8= 465X ( 8.2+29.6) - 365 X 37.8= 465X 37.8- 365 X

18、 37.8=(465- 365) X 37.8=100X 37.8= 378033 .【解答】解：(1) 0.1+0.2+0.3+0.4+ +0.9+0.1+0.11+0.12+ +0.98+0.99=(0.1+0.9) X (9+2) +0.1+ (0.11+0.99) X (99- 10) +2= 1X4.5+0.1+1.1X44.5= 4.6+ (0.1+1 ) X 44.5=4.6+4.45+44.5=9.05+44.5=53.5514T11(14y)X(l+1)34馬L =.a 1r =1x2CL* x (1+H蜷吟4 5上Oe 占 Q S=工 x -2(l+-)X(l+1)X- X(1A) n n+1原式=-Lx 2+-Lx -±-+-kx +L+-+2-x _±_ 2 3 3 4 4 59 10= 2 X (-+-+-+ + )2X3 3X4 4X59乂10= 2X (- -) + (- - -) + ( ) +-+)2 33 44 59 10=2X (-)2 1034.【解答】解：412+0.5 + 2= 412+ ( 0.5X2)= 412+ 1=