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ở đây , đều có mẫu số chung đấy bn , hoặc nếu ko cho sản , bn có thể biến đổi ra
a) 32.47 + 32.53
= 32(47 + 53)
= 32.100
= 3200
b) 37.7 + 80.3 + 43.7
= 7(37 + 43) + 80.3
= 7.80 + 80.3
= 80(7 + 3)
= 80.10
= 800
c) 113.38 + 113.62 + 87.62 + 87.38
= 113(38 + 62) + 87(62 + 38)
= 113.100 + 87.100
= 100(113 + 87)
= 100 . 200
= 20000
d) 123.456 + 456.321 - 256.444
= 456(123 + 321) - 256.444
= 456.444 - 256.444
= 444(456 - 256)
= 444.200
= 88800
e) 43.37 + 93.43 + 57.61 + 69.57
= 43(37 + 93) + 57(61 + 69)
= 43.130 + 57.130
= 130(43 + 57)
= 130.100
= 13000
a) 185+434+515+266+155 = (185+515)+(434+266)+155
= 700+700+155 = 1555
b. (652+148)+(327+73)+15=800+400+15=1215
c. (125*8)*(5*2)*1=1000*10*1=10000
d. (125*8)*(12*2)=1000*24=24000
e.3*25*4*2+4*37*6+2*38*12=600+888+912=2400
mik ik mik til lại cko nha! mấy bạn
a) 185 + 434 + 515 + 266 + 155
= ( 185 + 515 + 155 ) + ( 434 + 266 )
= 855 + 700
= 1555
b) 12 . 53 + 53 . 17 - 53 . 84
= 53 . ( 12 + 17 - 84 )
= 53 . ( - 55 )
= -2915
a, 185 + 434 + 515 + 266 + 155
= ( 185 + 515 + 155 ) + ( 434 + 266 )
= 855 + 700
= 1555
b, 12 . 53 + 53 . 17 - 53 . 84
= 53 . ( 12 + 17 - 84 )
= 53 . ( -55 )
= -2915
c, 19 . 128 + 36 . 82 + 64 . 69 + 64 .41
= 2432 + 2952 + 64 . ( 69 + 41 )
= 5384 + 64 . 110
= 5384 + 7040
= 12424
4:
a: \(\dfrac{\left(158-x\right)}{7}=20\)
=>\(158-x=7\cdot20=140\)
=>x=158-140=18
b: \(2x-138=23\cdot32\)
=>\(2x-138=736\)
=>2x=736+138=874
=>x=437
c: \(231-\left(x-6\right)=\dfrac{1339}{13}\)
=>\(231-\left(x-6\right)=103\)
=>x-6=128
=>x=128+6=134
d: \(10+2x=\dfrac{45}{43}\)
=>\(2x=\dfrac{45}{43}-10=-\dfrac{385}{43}\)
=>\(x=-\dfrac{385}{43}:2=-\dfrac{385}{86}\)
e: \(70-5\left(2x-3\right)=45\)
=>\(5\left(2x-3\right)=70-45=25\)
=>2x-3=5
=>2x=8
=>x=4
g: \(156-\left(x+61\right)=82\)
=>x+61=156-82=74
=>x=74-61=13
a, 277 + 113 + 323 + 87
= ( 277 + 323 ) + ( 113 + 87 )
= 600 + 200
= 800
b, 185 + 434 + 515 + 266 + 155
= ( 185 + 515 ) + ( 434 + 266 ) + 155
= 700 + 700 + 155
= 1400 + 155
= 1555
c, 8 . 12 . 125 . 2
= ( 125 . 8 ) . ( 12 . 2 )
= 1000 . 24
= 24000
d, 4 . 36 . 25 . 50
= ( 4 . 25 ) . ( 36 . 50 )
= 100 . 1800
= 180000
a, 277 + 113 + 323 + 87
= ( 277 + 323 ) + ( 113 + 87 )
= 600 + 200
= 800
b, 185 + 434 + 515 + 266 + 155
= ( 185 + 515 ) + ( 434 + 266 ) + 155
= 700 + 700 + 155
= 1400 + 155
= 1555
c, 8 . 12 . 125 . 2
= ( 125 . 8 ) . ( 12 . 2 )
= 1000 . 24
= 24000
d, 4 . 36 . 25 . 50
= ( 4 . 25 ) . ( 36 . 50 )
= 100 . 1800
= 180000
Bài 1 : Tính :
\(a)49-\left(-54\right)-23=103-23\)
\(=80\)
\(b)\left(-25\right).68+\left(-34\right).\left(-250\right)=-1700+8500\)
\(=6800\)
\(c)1999+\left(-2000\right)+2001+\left(-2002\right)=\left(-1\right)+\left(-1\right)\)
\(=-2\)
\(d)515+\left[72+\left(-515\right)+\left(-32\right)\right]=515+\left(-475\right)\)
\(=40\)
\(e)\left(2736-75\right)-2736+175=2661-2736+175\)
\(=100\)
\(g)-2020-\left(157-2020\right)-\left(-257\right)=-2020-\left(-1863\right)-\left(-257\right)\)
\(=100\)
Bài 1: Tính
a) Ta có: \(\left(-25\right)\cdot68+\left(-34\right)\cdot\left(-250\right)\)
\(=-25\cdot68+\left(-340\right)\cdot\left(-25\right)\)
\(=-25\cdot\left(68-340\right)\)
\(=-25\cdot\left(-272\right)\)
\(=6800\)
b) Ta có: \(1999+\left(-2000\right)+2001+\left(-2002\right)\)
\(=1999-2000+2001-2002\)
\(=-1-1=-2\)
c) Ta có: \(515+\left[72+\left(-515\right)+\left(-32\right)\right]\)
\(=515+72-515-32\)
\(=40\)
d) Ta có: \(\left(2736-75\right)-2736+175\)
\(=2736-75-2736+175\)
\(=100\)
e) Ta có: \(-2020-\left(157-2020\right)-\left(-257\right)\)
\(=-2020-157+2020+257\)
\(=100\)
Bài 2: Tìm x
a) Ta có: \(x-\left|-2\right|=\left|-18\right|\)
\(\Leftrightarrow x-2=18\)
hay x=20
Vậy: x=20
b) Ta có: \(2x-\left|+14\right|=\left|-14\right|\)
\(\Leftrightarrow2x-14=14\)
\(\Leftrightarrow2x=28\)
hay x=14
Vậy: x=14
c) Ta có: \(\left|x+4\right|+5=20-\left(-12-7\right)\)
\(\Leftrightarrow\left|x+4\right|+5=20+12+7\)
\(\Leftrightarrow\left|x+4\right|=39-5=34\)
\(\Leftrightarrow\left[{}\begin{matrix}x+4=34\\x+4=-34\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=30\\x=-38\end{matrix}\right.\)
Vậy: x∈{30;-38}
d) Ta có: \(15-\left|2-x\right|=\left(-2\right)^2\)
\(\Leftrightarrow15-\left|2-x\right|=4\)
\(\Leftrightarrow\left|2-x\right|=11\)
\(\Leftrightarrow\left[{}\begin{matrix}2-x=11\\2-x=-11\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-9\\x=13\end{matrix}\right.\)
Vậy: x∈{-9;13}
e) Ta có: \(\left|15-x\right|+\left|-25\right|=\left|-55\right|\)
\(\Leftrightarrow\left|15-x\right|+25=55\)
\(\Leftrightarrow\left|15-x\right|=30\)
\(\Leftrightarrow\left[{}\begin{matrix}15-x=30\\15-x=-30\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-15\\x=45\end{matrix}\right.\)
Vậy: x∈{-15;45}
g) Ta có: \(\left|17-\left(-4\right)\right|+\left|-24-\left(-5\right)\right|=\left|-x+3\right|\)
\(\Leftrightarrow\left|17+4\right|+\left|-24+5\right|=\left|3-x\right|\)
\(\Leftrightarrow\left|3-x\right|=40\)
\(\Leftrightarrow\left[{}\begin{matrix}3-x=40\\3-x=-40\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-37\\x=43\end{matrix}\right.\)
Vậy: x∈{-37;43}
Tính bằng cách hợp lý nha
Bài 1 :
a) 125.18 = 2250
b) 34.201 = 6834
c) 123.1001=123123
d) 15.302= 4530
i) 113.38 + 113.62 + 87.62 + 87.38
= 113(38+62) + 87(62+38)
= 113.100 + 87.100
=11300+8700
= 20000
e) 185 + 234 + 515 + 266 + 155
= ( 185 + 515 ) + (234 + 266 ) + 155
= 700 + 500 + 155
= 1355
f) 49.37 + 91.37 + 51.69
= 37 ( 49 + 91 ) + 51 . 69
= 37.140 + 51.69
=5180 + 3519
= 8699
Tk mk nha