Tính nhanh:
A.38/40x50/57 B.35/32x27/20+35/32x5/20
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`a) 465 + [ 58 + ( -465 ) + ( -38 ) ]`
`= 465 + 58 - 465 -38`
`= (465-465) + (58-38)`
`=0+ 20`
`=20`
`b) ( 35 - 17 ) + ( 17 + 20 - 35 )`
`= 35 -17 +17 +20-35`
`= (35-35) + (-17+17)+20`
`= 0 + 0 +20`
`=20`
b: \(305+\left(-105\right)+\left(-246\right)+546\)
\(=200+300\)
=500
c: \(435+\left(-43\right)+\left(-483\right)+\left(-57\right)+383+\left(-415\right)\)
\(=20-100-100\)
=-180
d: \(1316+317+\left(-1216\right)+\left(-315\right)+\left(-85\right)\)
\(=100-2-85\)
=13
a,= (45-35)+(-28+27+11)-6=10+10-6=14
b,=(305-105)+(-246+546)=200+300=500
c,= (435-415)+(-43-57)+(-483+383)=20-100-100=-180
d,=(1316-1216)+(317-315-85)= 100-83= 17
\(57\cdot25+57:\frac{1}{35}+114\cdot20\)
\(=57\cdot25+57\cdot35+2\cdot57\cdot20\)
\(=57\cdot\left(25+35+2\cdot20\right)\)
\(=57\cdot\left(25+35+40\right)\)
\(=57\cdot100\)
\(=5700\)
\(=57.25+57.35+57.2.20\)
\(=57.\left(25+35+60\right)\)
\(=57.100=5700\)
a) (-30) + 17 + (-70) + 33
=[-30+(-70)]+(17+33)
=-100+50
=-50
b) 56 - 15 - 6 + (-75)
=(56-6)-[15+(-75)]
=50-(-60)
=110
c) (157 - 56) - (44 + 57)
=157-56-44+57
=(-157-57)-(56+44)
=-100-100
=-200
d) (-24 + 174) - (174 - 24)
=-24+174-174+24
=(-24+24)+(174-174)
=0+0
=0
e) (35 - 47) - (-123 + 35) + [20 - (123 - 57)]
=35-47+123-35+[20-123+57]
=35-47+123-35+20-123+57
=(35-35)+(123-123)+(-47+57)
=0+0+(-10)
=-10
a: Ta có: \(\dfrac{8}{9}-\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+...+\dfrac{1}{72}\right)\)
\(=\dfrac{8}{9}-\left(1-\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{3}-...+\dfrac{1}{8}-\dfrac{1}{9}\right)\)
=0
1.73.(8-59)-59.(8-73)
=73.8-73.59-59.8-59.73
=73.(59-59)-8.(73-59)
=73.0-8.14
=0-112
=-112
2.159.(18-59)-59.(18 - 159)
=159.18-59.159-59.18-59.159
=159.(59-59)-18.(159-59)
=159.0-18.100
=0-1800
=-1800
a: =38/57x40/50=2/3x4/5=8/15
b: =35/32(27/20+5/20)=35/32x32/20=35/20=7/4
a, `5/6` b, `7/4`