《五年级口算、速算天天练》参34-50 34、观察物体
720+180 = 900 0.36÷4 = 0.09 7.8×5×2 = 78
298×2 = 596 4.2-0.8 = 3.4 320×50÷25 = 0 0.8×3 = 2.4 4.6÷2 = 2.3 0.125×5.9×8 = 5.9
0.4×300 = 120 0.46÷2 = 0.23 21×45÷7 = 135 0.6×0.6 = 0.36 8.8÷4 = 2.2 2.8+1.6+0.4 = 4.8 0.5×101 = 50.5 72×125 = 9000 5×7+39 = 74 0.84÷6 = 0.14 3.81×2 = 7.62 0.125×15×8 = 15 123×5 = 615 0.4×200 = 80 2.5×44 = 110
5.4÷0.9 = 6 9.6×0.5 = 4.8 0.6×0.5×30 = 9 0.8÷0.2 = 4 2.45÷0.01 = 245 17×28+28×83 = 2800 0×4.25 = 0 50×3.2 = 160 -32.4-1
6.6 = 5 695-474 = 221 52×99 = 5148 15×4×0.7 = 42 0.32÷0.32 = 1 4.8×3 = 14.4 99×0.61+0.61 = 61 0.25×2 = 0.5 7.2×5 = 36 1.2÷0.2×50 = 300 3.25×4 = 13 0.35×100 = 35 1.25×32×25 = 1000
0÷6.48 = 0 0.63÷30 = 0.021 2.4×(5+5) = 24 63×90 = 5670 4.5×0.1 = 0.45 13×25×4 = 1300
3.2÷4 = 0.8 324÷100 = 3.24 1300-700+500 = 1100 308-48 = 260 7×0.6 =
4.2 420÷6÷7 = 10
24×25 = 600 1.24×4 = 4.96 43×4×5 = 860 数奥同步学答案
右图(略)中有 60 个长方形(应为“矩形”,否则总数中应减去正方形个数)。(4+3+2+1) × (3+2+1) = 60 (个)
练29 三、观察物体
0.42÷0.07 = 6 0.5×101 = 50.5 0.48+3.52-3 = 1
52×99 = 5148 9.6×0.5 = 4.8 9×0.4÷6 = 0.6 0.63÷30 = 0.021 7.3÷7.3 = 1 63×30÷30 = 63 30×3.5 = 105 324÷100 = 3.24 30÷0.1÷60 = 5 5.4÷0.9 = 6 7×0.6 = 4.2 4.2-3.6+0.4 = 1
0.35×100 = 35 69.1-47.4 = 21.7 120×25÷5 = 600 7.8×6 = 46.8 4.8×3 = 14.4 6.5÷5×4 = 5.2 1.5×9.9 = 14.85 0.36÷4 = 0.09 1.8×15÷3 = 9 4.5×0.1 = 0.45 123×5 = 615 (0.17-0.09)÷0.2 =0.4 3.8×9.9 = 37.62 24×25 = 600 6.28+3.72+10 = 20 0.84÷6 = 0.14 72×125 = 9000 2.5×32×1.25 = 100 0.35×100 = 35 0.6×0.6 = 0.36 6×0.14÷3 = 0.28 4.2-0.8 = 3.4 1.24×4 = 4.96 6×3.1÷20 = 0.93 7×0.6 = 4.2 3.25×4 = 13 45×30÷5 = 270 0.8×3 = 2.4 8.8÷4 = 2.2 4.2×20÷6 = 14 4.6÷2 = 2.3 0.25×2 = 0.5 50×0.04×0.1 = 0.2 4.5×0.1 = 0.45 50×3.2 = 160 3.6+6.4+7 = 17 0×4.25 = 0 3.81×2 = 7.62 12.5×0.8×10 = 100 0.46÷2 = 0.23 0.4×200 = 80 0.42×200÷4 = 21 3.2×4 = 12.8 63×90 = 5670 10+7.84+19 =36.84 数奥同步学答案
图(略),正方体的六个面上A、B、C、D、E、F排列顺序完全相同,那么A的对面是 D ,B的对面是 F ,C的对面是 E 。
从图上可知A与B、C、E、F相邻,故A的对面只能是D;再根据相对方位可以推出E、F的位置。
练30 三、观察物体
2.45÷0.01 = 245 4×250 = 1000 4.26×10÷2.13 = 20 20-7.6 = 12.4 26×9.9 = 257.4 2.4÷0.24+1 = 11 9.8+9.9 = 19.7 4×0.02 = 0.08 4.5×7.8÷7.8 = 4.5 4.3×101 = 434.3 2÷5 = 0.4 4.5÷9×0.5 = 0.25 36÷600 = 0.06 4.8÷0.08 = 60 5×(0.4+0.8) = 6
4.8×5 = 24 4.8÷0.08 = 300 3.26×10÷2 = 16.3 425-199 = 226 15.7-3.7 = 12 40×32÷20 = 4.8+3.9 = 8.7 1÷4 = 0.25 48×5-200 = 40 920-105 = 815 4.5×101 = 4.5 0.×9÷3 = 1.62 1.9×8 = 15.2 3.45+0.55 = 4 6.3÷3.5×3.5 = 6.3 3.21+ 2.29 = 5.5 30÷60 = 0.5 2.05×9+2.05 = 20.5 5.77-3.66 = 2.11 7.8+2.2 = 10 7.8×99+7.8 =780 30×3.5 = 105 4.9+7.1 = 12 36×12×0.5 =216
523-275 = 248 2.7×30 = 81 4.5×101-4.5 = 450 0.32÷0.08 = 4 13×0.5 = 6.5 3.4-0.6-0.4 = 2.4 7.8÷6 = 1.3 9.8+8.7 = 18.5 0.6+5.4÷6 = 1.5
604÷4 = 151 7.8÷3 = 2.6 50.6-24-16 = 10.6 4×1.2 = 4.8 50.5-22.7 = 27.8 3.42-2.48+6.58 =7.52 0.84÷6 = 0.14 18.3-16.4 = 1.9 418-52×4 = 210 4.7-3.9 = 0.8 0.6×0.12 = 0.072 1.36+ 5.4+0. = 7.4 数奥同步学答案
图(略),正方体的六个面上分别写有A、B、C、D、E五个字母,其中有两个面字母相同,根据下面的三个视图,可以断定 C 被写了两遍。
从图上可知A与B、C、E、F相邻,故A的对面只能是D;再根据相对方位可以推出E、F的位置。
练31 三、观察物体
0.125×8 = 1 2.8÷0.04 = 70 0.63÷0.9-0.5 = 0.2 4.9-1.9 = 3 6.44+7.42 = 13.86 19.9-7.9+2.5 = 14.5 4×0.02 = 0.08 1.48+0.26 = 1.74 51×101-51 = 5100 3.4×100 = 340 0.4×0.5 = 0.2 4÷5+ 4.6 = 5.4
5.4÷0.06 = 90 1.6×2.5 = 4 329-108-129 = 92
7.2÷0.08 = 90 9.9÷0.3 = 33 4.7×99+4.7 = 470 6.24÷1.04 = 6 5.77+4.68 = 10.45 6×600÷90 = 40 5.4÷0.9 = 6 42-4.2 = 37.8 0.36×5÷4 = 0.45 304÷4 = 76 36.5-24.1 = 12.4 9.3÷3×2 = 6.2 47.6÷2 = 23.8 45×1.1 = 49.5 27×4+27×16 = 0 14.5-3.7 = 10.8 9.04-8.42 = 0.62 7.2÷4.5÷2 = 0.8 12.6-0.6 = 12 780÷30 = 26 0.5×40×1.3 = 26 84÷4 = 21 570÷30 = 19 0.9×0.4×5 = 1.8
506-109 = 397 9÷0.03 = 300 0.04÷0.08-0.4 =0.1 950-280 = 670 10-6.4 = 3.6 1.25×7.6×8 = 76 740-180 = 560 56÷80 = 0.7 5.6×101-5.6 = 560 700-238 = 462 40÷0.01 = 4000 65.8-39.9-10.1 =15.8 24.5×0.1 = 2.45 70÷10 = 7 18.3÷2÷5 = 1.83 3.4-1.8 = 1.6 6.3+1.8 = 8.1 700-620+305 =385 92.7-82.3 = 10.4 41×99 = 4059 4.5×2÷5 = 1.8 数奥同步学答案
图(略),在正方体的八个顶点中选出四个,使它们中的任何三个构成的三角形
都是等边三角形。
等边三角形的三边等长,从图上可知这个边长应该是任一面上的对角线。
因此四点组合有:ACFH以及DBEC。 练32 四、简易方程
1、设长方形的长是a,宽是b,周长为C,面积为S,那么: 周长公式:C=(a+b)×2面积公式:S=a×b
2、设正方形的边长是a,周长为C,面积为S,那么: 周长公式:C=4a面积公式:S=a2
3、设路程为s,速度为v,时间为t,那路程、时间、速度之间的关系用字母
可表示为 s=vt 。
4.5+1
5.5 = 20 252÷4 = 63 4.8-0.4-0.6 = 3.8 3.7×3 = 11.1
4.8÷0.6 = 8 0.48÷8×10 = 0.6 4.8×5 = 24 21×90 = 10 -3 5.2-4.8 = 14
4.8÷4 = 1.2 9.8×5 = 49 0.8×0.5+4 = 4.4 0.8+1.4 = 2.2 58×0.6 = 34.8 4.8÷6÷0.8 = 1 7.6×4 = 30.4 24-15.2 = 8.8 2.4÷6÷0.2 = 2 240+190 = 430 1.3+0.9 = 2.2 1.4×20×0.5 = 14 69×30 = 2070 4.2+0.6 = 4.8 0.25×4.32×4 =4.32 10-7.2 = 2.8 88×1.1 = 96.8 2.5×1.73×4 = 17.3 15.9-2.7 = 13.2 8.9-6.8 = 2.1 0.3÷0.15÷4 = 0.5 17.4+32.6 = 50 23.2-18.4 = 4.8 12.5+56.2-60 = 8.7 186÷4 = 46.5 5.6×99 = 5.4 9.26×1.25×8 =92.6 32.5÷5 = 6.5 3.6×2.5×0.4 = 3.6 18×9.9 = 178.2 24×9.9 = 237.6 2.8÷0.4 = 7 2.5×24×4 = 240 数奥同步学答案
在下题的方格中填上一个合适的数,使等式成立。 [(□1+9)×9-9]÷9=9 (9×9+9)÷9-9=1 练33 四、简易方程 省略乘号写出下面各式 a×x= ax b×8 = 8b 12= 1 x×x = x2b×1 = 1b 22= 4 3×a = 3a c·9 = 9c 32= 9 x×4 = 4x 5·q = 5q 42= 16 a×b = ab 7·k = 7k 52= 25 a×8 = 8a 12·c = 12c 62= 36 b×b = b23·a = 3a 72= 49
a×1 = 1a 1×c = 1c 82= 4×a = 4a 1·b = 1b 92= 81 t×8 = 8t 5·d = 5d 102= 100 a·c = ac 6·k = 6k 112= 121 s·t = st 7·k = 7k 122= 144 8·a = 8a x·6 = 6x 132= 169 x·8 = 8x z·9 = 9z 142= 196 a·5 = 5a y·10 = 10y 152= 225 b·10 = 10b 8×x = 8x 162= 256 8·c = 8c a×2 = 2a 172= 2 12·b = 12b 6×r = 6r 182= 324 5·c = 5c 8×y = 8y 192= 361 202= 400 数奥同步学答案
规定 a*b=a+(a+1)+(a+2)+…(a+b+1) (a、b均为自然数b>a)。如果a*10=72,a= 2.7 。
72=10a+(1+2+3+4+5+6+7+8+9)=10a+45 10a=72-45=27 a=2.7 练34 四、简易方程
3x+6x= 9x 12x+1.2x = 13.2x 3x+4x+3x =10x b+4b = 5b 4.2t-t = 3.2t 4.8x+x+1.2x =7x x+x = 2x 1.5a-0.9a = 0.6a 7x+4x-5x = 6x 18x-9x = 9x 7.8x+2.2x = 10x b-0.3b = 0.7b x×2 = 2x 9a-6a = 3a 6x-3x+2x = 5x 7b-7b = 0 3.6a+4.4a = 8a 9x-5x = 4x 3x+4.5x = 7.5x 17x+14x = 31x 7.2x-2.2x = 5x 7b-4b = 3b 9.05t-2.15t = 6.9t 3.7x+ 6.5x =10.2x 5.2a-3.2a = 2a 3.5b+b = 4.5b a+4a = 5a x+5x = 6x 1.7x-1.4x = 0.3x 3.6x- 1.2x =2.4x 4.5a-2.1a = 2.4a 8.6x-5x = 3.6x 7.2x-4.2x = 3x
18x-14x = 4x 4.8b+3.2b = 8b 7.8t-5.3t = 2.5t 15b-7.5b = 7.5b 5b+3b = 8b 3.2x+4.8x = 8x 8x+5x = 13x 5.6a-3.6a = 2a 9a+0.03a = 9.03a
a+a = 2a 0.27t+2.33t = 2.6t 3.6b+4.4b = 8b 4a+6a = 10a 2a+4a = 6a 3.4x+2.6x = 6x
b-0.5b = 0.5b 5x+4x = 9x 4.8a+a = 5.8a 2a×2.5 = 5a 7x+3.4x = 10.4x 1.2x-x = 0.2x 7.5y-5y = 2.5y 15x-7x = 8x 8x-4x = 4x 9.2x+0.8x = 10x 8x-4x = 4x 15x-7.5x = 7.5x 数奥同步学答案
如果一个数与它自己相加、相减、相除其和、差、商相加的和为8.6,那么它是 3.8 。
( 8.6-1-0 ) ÷ 2 = 3.8 练35 四、简易方程 把方程圈出来
x+3 = 6 8x < 5 5x = 0 5-x < 5 9x > 8 8x+8 < 17 3.2x-x = 1.6 2y+3y = 152 85 > 2x
4.8+3.9 = 8.7 5500÷500 = 11 506-109+3 = 400 0×320 = 0 5.4-2.3 = 3.1 3400-2000÷2 =2400 720÷18 = 40 3.6÷3.6 = 1 13÷5÷1.3 = 2
31÷0.1 = 310 1.1× = 59.4 700-238-262 = 200 7.6×9.9 = 75.24 409+324 = 733 0÷16×5 = 200
0÷420 = 0 430÷10 = 43 420×2÷70 = 12
44×2.5 = 110 5.77-3.66 = 2.11 40.5-13.5+20.5 = 47.5 4.21+
5.59 = 9.8 960+105 = 1065 16×4÷8 = 8
28×1.1 = 30.8 430÷0.01 = 43000 324×11÷11 = 324 420÷20 = 21 4.8+3.2 = 8 8.7+6.9+4.4 = 20 240-80 = 160 3.6÷0.1 = 36 750÷5÷30 = 5
3600÷180 = 20 1200÷300 = 4 31.9+21.1-10 = 43 6300÷90 = 70 45÷900 = 0.05 520÷13÷8 = 5
28×11 = 308 2.48-0.08 = 2.4 1400÷700×5 = 10 数奥同步学答案
某数减去8再乘以4最后加上7,得11,那么这个数先加上7再乘以4最后减去8,得 56 。
( 11 - 7 ) ÷ 4 + 8 = 9 ( 9 + 7 ) × 4 - 8 = 56 练36 四、简易方程
480÷6 = 80 700÷20 = 35 0.32×0.5 = 0.16 5.6÷70 = 0.08 300×0.03 = 9 5.5÷5×80 = 88
87×9.9 = 861.3 4500÷500 = 9 400+4000-800 = 3600 400-173 = 227 550÷1.1 = 500 4.48÷4.48×0.1 = 0.1 45÷0.1 = 450 1.9×30 = 57 4.8÷48÷0.01 = 10 9.2-4.8 = 4.4 00÷600 = 9 400÷50÷80 = 0.1 0÷40 = 16 3.6×101 = 363.6 24.3+17.7-12 = 30 360÷40 = 9 3.6×4-4.8 = 9.6 3.2÷0.01÷40 = 8 420÷21 = 20 0.×3 = 1.62 4×0.25÷0.5 = 2
1.1×36 = 39.6 24×50 = 1200 5.94- 3.48- 1.52 =0.94 570÷30 = 19 42×1.1 = 46.2 3.2×100÷80 = 4 320÷3.2 = 10 349-198 = 151 80×200÷400 = 40 24-12.5 = 11.5 13.4-11.6 = 1.8 7×0.9÷0.7 = 9 0÷4.8 = 0 0÷400 = 0 3.25×0÷25 = 0 1.38+2 2.2 = 2
3.58 3.11×6 = 18.66 400+560-298 = 662
箱子里装有同样数目的乒乓球和羽毛球,每次取出5个乒乓球和3个羽毛球,取了若干次后,乒乓球没有了,羽毛球还剩6个。问一共取了几次(列方程解)解:设乒乓球总数为a,取球次数为b。则 a=5b a=3b+6
5b=a=3b+6 5b=3b+6 2b=6 b=3
答:一共取了3次。 数奥同步学答案
有面额5元和10元的人民币共43张,合计340元,那么5元币 18 张,10元币 25 张。
解:设5元币有f张,10元币有t张,则 f+t=43 5f+10t=340 10f+10t=430
10f-5f=430-340 5f=90
f=18 t=43-18=25 练37 四、简易方程 解方程:
x÷8 = 125 6x÷5 = 12 x÷0.05 = 60
解x = 125×8 解 6x = 60 解x = 60×0.05 x = 1000 x = 10 x = 3
x÷0.8 = 10 0.05x = 3.5 x-3.8 = 6.2
解x = 10×0.8 解 x = 3.5÷0.05 解x = 6.2+3.8 x = 8 x = 70 x = 10
3x = 42 x-4.8 = 5.2 43-x = 38
解x = 42÷3 解 x = 5.2+4.8 解 x = 43-38 x = 14 x = 10 x = 5
40÷x = 8 x+4.2 = 7.8 27.2÷x = 6.8 解x = 40÷8 解 x = 7.8-4.2 解 x = 27.2÷ 6.8
x = 5 x = 3.6 x = 4
50×x = 350 2.3x = 6.9 2.5x = 60
解x = 350÷50 解 x = 6.9÷2.3 解 x = 60÷2.5 x = 7 x = 3 x = 24
450÷x = 90 3.5÷x = 0.7 x+15 = 41
解x = 450÷90 解 x = 3.5÷0.7 解 x = 41-15 x = 5 x = 5 x = 26
使方程左右两边相等的未知数的值,叫做方程的解。 数奥同步学答案
登山比赛中,小明上山时平均每分钟走40米,18分钟到达山顶。然后原路返回,平均每分钟走60米。小明上山时平均每分钟走 48 米。
[ ( 40×18 ) × 2 ] ÷ [ 18 + ( 40×18 )÷ 60 ] = 48 (米/分) 练38 四、简易方程 解方程:
x÷4.5 = 1.2 0.9x = 2.7 x-21 = 14
解x = 1.2×4.5 解 x = 2.7÷0.9 解 x = 14+21 x = 5.4 x = 3 x = 35
6.98-x = 6.7 0.8÷x = 10 47+x = 47
解x = 6.98-6.7 解 x = 0.8÷10 解 x = 47-47 x = 0.28 x = 0.08 x = 0
2.5x = 7.5 x-45 = 1000 6x = 42
解x = 7.5÷2.5 解 x = 1000+45 解 x = 42÷7 x = 3 x = 1045 x = 6
x+0.8 = 1.2 3x = 45 x÷7 = 12
解x = 1.2-0.8 解 x = 45÷3 解 x = 12×7 x = 0.4 x = 15 x = 84
x+21.5 = 34 1.6x = 3.36 24 x = 96
解 x = 34-21.5 解 x = 3.36÷1.6 解 x = 96÷24 x = 12.5 x = 2.1 x = 4
x-0.32 = 8.6 x+20 = 35 x-19 = 2 解x = 8.6+0.32 解 x = 35-20 解 x = 2+19
x = 8.92 x = 15 x = 21 求方程的解的过程,叫做解方程。 数奥同步学答案
甲、乙两城相距350千米,一艘客轮在其间往返航行,从甲城到乙城是顺流,用去10小时;从乙城返回甲城是逆流,用去14小时。那么船在静水中的时速是30千米,水流时速是5千米。
解:设船在静水中的时速是c,水流时速是s 则(c+s)×10 = (c-s)×14 = 350 10c+10s = 14c-14s 4c = 24s c = 6s
(c+s)×10 = 350 (6s+s)×10 = 350 7s×10 = 350 s = 350÷70 = 5 c = 6s = 6×5 = 30 练39 四、简易方程
解方程:(以下由于“解”不好打印出来所以省略,同学们做题一定要写“解”
5x+6 = 10 7x-26 = 2 5x-39 = 56
解5x = 10-6 7x = 2+26 解 5x = 56+39 x = 4÷5 x = 28÷7 x = 95÷5
x = 0.8 x = 4 x = 19
16+4x = 76 3x+4 = 40 3.2x+4.8x = 80 4x = 76-16 3x = 40-4 8x = 80
x = 60÷4 x = 36÷3 x = 80÷8 x = 15 x = 12 x = 10 1.2x+
2.8x = 10.4 12x-9x = 4.2 10x-6x = 40 4x = 10.4 3x = 4.2 4x = 40 x = 10.4÷4 x = 4.2÷3 x = 40÷4 x = 2.6 x = 1.4 x = 10
4x-2.6 = 1.4 6x+3 = 9 3 x+8x = 55 4x = 1.4+2.6 6x = 9-3 11x = 55
x = 4÷4 x = 6÷6 x = 55÷11 x = 1 x = 1 x = 5
0.92-8x = 0.52 4x-2 = 10 4.2x-1.9x = 4.6
8x = 0.92-0.52 4x = 10+2 2.3x = 4.6 x = 0.4÷8 x = 12÷4 x = 4.6÷ 2.3
x = 0.05 x = 3 x = 2
4.5 x+2.5x = 1.19 18+15x = 21 8x-4×14 = 0 7x = 1.19 15x = 21-18 8x = 56 x = 1.19÷7 x = 3÷15 x = 56÷8 x = 0.17 x = 0.2 x =7 数奥同步学答案
王老师买2千克橘子和3千克香蕉,共用 5.7元。买7千克橘子和3千克香蕉,共用11.7元。那么1千克橘子 1.2元,1千克香蕉1.1元。
解:设1千克橘子j元,1千克香蕉x元 则2j+3x = 5.7 7j+3x = 11.7 x = (5.7-2×1.2)÷3 5j = 6 x = 3.3÷3 j = 6÷5 x = 1.1 j = 1.2 解方程:
15x-7.5x = 22.5 1.2x-x = 6 y+3y = 36 7.5x = 22.5 0.2x = 6 4y = 36 x = 22.5÷7.5 x = 6÷0.2 y = 36÷4 x = 3 x = 30 y = 9
22.1x+27.9x = 200 3.4x+2.6x = 7.2 6x-3x = 4.8
50x = 200 6x = 7.2 3x = 4.8 x = 200÷50 x = 7.2÷6 x = 4.8÷3
x = 4 x = 1.2 x = 1.6
9x-5x = 6.4 5x+7x = 42 3m+2m = 65 4x = 6.4 12x = 42 5m = 65
x = 6.4÷4 x = 42÷12 m = 65÷5 x = 1.6 x = 3.5 m = 13
3.5 x+6.5x = 1 4x-7.2 = 10 3 x+x = 180 10x = 1 4x = 10+7.2 4x = 180 x = 1÷10 x = 17.2÷4 x = 180÷4 x = 0.1 x = 4.3 x = 45 3.6x-1.2x =
4.8 0.8÷x = 10 5y+y = 96 2.4x = 4.8 10x = 0.8 6y = 96 x = 4.8÷2.4 x = 0.8÷10 y = 96÷6 x = 2 x = 0.08 y = 16
8x-4x = 20 x-45 = 1000 y+y = 33 4x = 20 x = 1000+45 2y = 33
x = 20÷4 x = 1045 y = 33÷2 x = 5 y = 16.5 数奥同步学答案
一列火车通过530米长的隧道要40秒,以同样的速度通过380米的大桥要用30秒钟,这列火车的速度是 15 米/秒,车长是 70 米。
解:设火车的速度是V米/秒,车长是L米 则V = (530-380) ÷ (40-30) = 15 L = 40×15 - 530 = 70 解方程:
5x+8 = 10 11 x-4.5 = 17.5 21x-10x = 0.66 5x = 10-8 11x = 17.5+4.5 11x = 0.66 x = 2÷5 x = 22÷11 x = 0.66÷11 x = 0.4 x = 2 x = 0.06
x÷18 = 720 6.3+0.2x = 16.3 9x-6x = 4.8 x = 720×18 0.2x = 16.3-6.3 3x = 4.8
x = 12960 x = 10÷0.2 x = 4.8÷3 x = 50 x = 1.6
150+x = 420 8.6÷x = 17.2 0.8x+20 = 24 x = 420-150 17.2x = 8.6 0.8x = 24-20
x = 270 x = 8.6÷17.2 x = 4÷0.8
x = 0.5 x = 5 3.2+x = 4.8 x-4.9 = 1 5.8 13 x-10x = 0.96
x = 4.8-3.2 x = 15.8+4.9 3x = 0.96 x = 1.6 x = 20.7 x = 0.96÷3
x = 0.32
x-250 = 750 1.2x-x = 6 x+3x = 72 x = 750+250 0.2x = 6 4x = 72
x = 1000 x = 6÷0.2 x = 72÷4 x = 30 x = 18
x×8 = 1000 10 x-8x = 20 1.6+ 2.2x =10.4 x = 1000÷8 2x = 20 2.2x =10.4-1.6 x = 125 x = 20÷2 x = 8.8÷2.2 x = 10 x = 4 数奥同步学答案
甲乙两辆车同时从两地相对开出,甲车平均每小时行60千米,乙车平均每小时行55千米,相遇时,甲车比乙车多行45千米,则两地相距 1035 千米。
解:45 ÷ (60-55) = 9 (小时) 9 × ( 60+55 ) = 1035 (千米) 练42 四、简易方程 解方程: 1.6x+
2.4x = 10.4 435-x = 305 x-3 = 6 4x = 10.4 x = 435-305 x = 6+3 x = 10.4÷4 x = 130 x = 9 x = 2.6
8x-1.8 = 30.2 30.4+x = 40 9÷x = 1.5 8x = 30.2+1.8 x = 40-30.4 x = 9÷1.5
x = 32÷8 x = 9.6 x = 6 x = 4
x+2x = 66 0.07x = 3.5 8x-3x = 105 3x = 66 x = 3.5÷0.07 5x = 105
x = 66÷3 x = 50 x = 105÷5 x = 22 x = 21
56x-50x = 36 0.9x = 8.1 x-35 = 40 6x = 36 x = 8.1÷0.9 x = 40+35
x = 36÷6 x = 9 x = 75 x = 6
x+1.8 = 3.2 x+35 = 91 40-3x = 13 x = 3.2-1.8 x = 91-35 3x = 40-13 x = 1.4 x = 56 x = 27÷3
x = 9
x×30 = 69 x×3 = 57 6x-x = 125 x = 69÷30 x = 57÷3 5x = 125
x = 2.3 x = 19 x = 125÷5 x = 25 数奥同步学答案
甲乙两辆车同时从A、B两地相向而行,在距B地千米处相遇。他们各自到达对方车站后立即返回原地,途中又在距A地42千米处相遇。两次相遇地点间的距离为 24 千米。
解:设A、B两城间距为S千米,两次相遇点间距为L
首次相遇时两车合起来走了A、B两城间距(S),其中乙车走了千米;
再次相遇时两车合起来共走了S的三倍,那么乙车也应该走了千米的
三倍;但我们知道乙车实际走了A、B两城间距(S)加上折返的42千米。
所以:×3 = S+42 S = 162-42
S = 120 (千米)
两次相遇点间距等于A、B两城间距减去相遇点到两头的距离,即: L = S――42 = 120――42 = 24 (千米) 单元检测
2.5×0.04 = 0.1 0.42÷0.07 = 6 0.25×9×4 = 9 10-4.28 = 5.72 3.2×1.1 = 3.52 5.6×101-5.6 = 560 2.8÷0.7 = 4 2.8÷0.4 = 7 4.2÷0.7÷0.1 = 60 101×3.2 = 323.2 4.6×101 = 4.6 5.6÷0.8÷7 = 1 ÷60 = 0.9 27×9.9 = 267.3 1÷0.25×0.4 = 1.6 3.6×1.1 = 3.96 5.6÷0.8 = 7 0.3÷0.01÷10 = 3 0.36÷0.06 = 6 7.5÷2.5 = 3 4.8÷6÷0.8 = 1 0.84÷6 = 0.14 1.6×2.5 = 4 20×1.4×0.5 = 14 3.25×4 = 13 2.5×2.4 = 6 0.75÷0.5×6 = 9 2.125×8 = 17 1.25×16 = 20 0.6+0.4÷2 =0.8 3.5÷0.07 = 50 1.25×24 = 30 2.6×9.9+2.6×0.1 = 26 4.8×0.5 = 2.4 12.5×32 = 400 0.5×4÷0.5×4 = 16 0.57÷0.19 = 3 1÷0.125 = 8 2.5×32×1.25 = 100 4.73÷4.3 = 1.1 10÷0.25 = 40 1.7×2.8+1.7×7.2 = 17 解方程:
x÷8 = 1.25 0.25x = 10 16÷x = 3.2 x = 1.25×8 x = 10÷0.25 3.2x = 16
x = 10 x = 40 x = 16÷3.2 x = 5 2.5x = 7.5
3.6x+6.4x = 1 12x-6.5x = 11 x = 7.5÷2.5 10x = 1 5.5x = 11 x = 3 x = 1÷10 x = 11÷5.5 x = 0.1 x = 2 算法技巧解析 P.50
自主训练
44÷0.5 1.32÷0.5 21÷0.25 132÷0.5 = 44×2 = 1.32×2 = 21×4 = 132×2 = 88 = 2. = 84 = 2
1.7÷0.2 3.21÷0.25 1.24÷0.125 0.4÷0.125
= 1.7×4 = 3.21×4 = 1.24×8 = 0.4×8 = 6.8 = 12.84 = 9.92 = 3.2
23÷0.5 50÷0.125 2.4÷0.25 3÷0.125 = 23×2 = 50×8 = 2.4×4 = 3×8 = 46 = 400 = 9.6 = 24 P.51 自主训练 1、
(4.8×7.5×8.1) ÷ (2.4×2.5×2.7) = (4.8÷2.4) × (7.5÷2.5) × (8.1÷2.7) = 2×3×3 = 18 2、
(3.2×2.8×6.4) ÷ (0.8×0.7×0.4) = (3.2÷0.8) × (2.8÷0.7) × (6.4÷0.4) = 4×4×16 = 256 3、
(10个0.625,11个8,以及12个2连乘) (0.625×0.625×...×0.625)×(8×8×...×8)×(2×2× (2) = (0.625×8×2)10× 8 × 2×2 = 1010×8×4 = 10000000000×32 = 320000000000
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