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1)
\(45\left(13+78\right)+9\left(87+22\right)5\)
\(=45\left(13+78\right)+45\left(87+22\right)\)
\(=45\left(13+78+87+22\right)\)
\(=45\left[\left(87+13\right)+\left(78+22\right)\right]\)
\(=45\left[100+100\right]\)
\(=45.200\)
\(=9000\)
2)
\(43+37+93.43+57.61+69.57\)
\(=43\left(37+93\right)+57.\left(61+69\right)\)
\(=43.130+57.130\)
\(=130\left(43+57\right)\)
\(=130.100\)
=13000
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1.
a.
11 + x : 5 = 13
x : 5 = 13 - 11
x : 5 = 2
x = 2 . 5
x = 10
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5: \(=42\cdot\left(15+96+25+4\right)=42\cdot140=5880\)
6: \(=45\left(13+78+87+22\right)=45\cdot200=9000\)
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7)
53.(51+4)+53.(49+96)+53
=53.55+53.145+53
=53.(55+145+1)
=53.201
=10653
8)
42.(15+96)+6.(25+4).7
=42.111+(6.7).29
=42.111+42.29
=42.(111+29)
=42.140
=5880
9)
45.(13+78)+9.(87+22).5
=45.91+(9.5).109
=45.91+45.109
=45.(91+109)
=45.200
=9000
10)
16.(27+75)+8.(53+25).2
=16.102+(8.2).78
=16.102+16.78
=16.(102+78)
=16.180
=2880
7)
53.(51+4)+53.(49+96)+53
=53.55+53.145+53
=53.(55+145+1)
=53.201
=10653
8)
42.(15+96)+6.(25+4).7
=42.111+(6.7).29
=42.111+42.29
=42.(111+29)
=42.140
=5880
9)
45.(13+78)+9.(87+22).5
=45.91+(9.5).109
=45.91+45.109
=45.(91+109)
=45.200
=9000
10)
16.(27+75)+8.(53+25).2
=16.102+(8.2).78
=16.102+16.78
=16.(102+78)
=16.180
=2880
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a)45.(13+78)+9.(87+22).5
=45.91+(9.5).109
=45.91+45.109
=45.(91+109)
=45.200
=9000
b) 16.(27+75)+8.(53+25).2
=16.102+(8.2).78
=16.102+16.78
=16.(102+78)
=16.180
=2880
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39x[250+87]+64x[240+97]
=39x337+64x337
=(39+64)x337
=103x337
=34711
78x31+78x24+78x17-22x72
=78x(31+24+17)-22x72
=78x72-22x72
=(78-22)x72
=56x72
=4032
bn tính lại nha
39 x [ 250 + 87 ] + 64 x [ 240 + 97 ]
= 39 x 337 + 64 x 337
= 337 x ( 39 + 64 )
= 337 x 103
= 34711
bai tiep
78 x 31 + 78 x 24 +78 x 17 - 22
= 78 x ( 31 + 24 + 17 ) - 22 x 72
= 78 x 72 - 22 x 72
=72 x ( 72 - 22 )
= 72 x 50
= 3600
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a) 2 x 53 x 12 + 4 x 6 x 87 - 3 x 8 x 40 = 53 x 24 + 24 x 87 - 24 x 40
= 24 x ( 53 + 87 - 40 )
= 24 x 100
= 2400.
b) 78 x 31 + 78 x 24 + 78 x 17 + 22 x 72 = 78 x ( 31 + 24 + 17 ) + 22 x 72
= 78 x 72 + 22 x 72
= 72 x ( 78 + 22 )
= 72 x 100
= 7200.
c) Cách 1. Ta có : 4-2=2 ; 6-4=2 ; 8-6=2 ; ... ; 100-98=2.
=> Đây là một dãy số cách đều 2 đơn vị.
Dãy số trên có số số hạng là : ( 100 - 2 ) : 2 + 1 = 50 ( số hạng )
Tổng dãy số là : ( 100 + 2 ) x 50 : 2 = 2550
Cách 2. A = 2 + 4 + 6 + 8 + ... + 98 + 100
A = 1x2 + 2x2 + 3x2 + 4x2 + ... + 49x2 + 50x2
A = ( 1 + 2 + 3 + 4 + ... + 49 + 50 ) x2
A = 1275 x 2
A = 2550.
Đáp số : a) 2400
b) 7200
c) A = 2550.
a) 2 x 53 x 12 + 4 x 6 x 87 - 3 x 8 x 40
= 24 x 53 + 24 x 87 - 24 x 40
= 24 x ( 53 + 87 - 40 )
= 24 x 100
= 2400
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3:
a: -5x-16=-46
=>-5x=-46+16=-30
=>5x=30
=>\(x=\dfrac{30}{5}=6\)
b: -80-(-16-x)=20
=>\(-x-16=-80-20=-100\)
=>x+16=100
=>x=100-16=84
2:
a: \(\left(45-3456\right)+3456\)
\(=45+3456-3456\)
=45
b: \(\left(77+22-75\right)-\left(-25-78-13\right)\)
\(=77+13+22+78-75+25\)
\(=90+100-50\)
=140
c: \(-25\cdot63-25\cdot37\)
\(=-25\left(63+37\right)\)
\(=-25\cdot100=-2500\)
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\(a.13.\left(78+22\right)=13.100=1300\)
\(b.25.70+28.25+25.2=25.\left(70+28+2\right)=25.100=2500\)
\(c.\dfrac{15.3.14.2.19}{19.14.15}=6\)
\(d.\dfrac{132.70.60}{12.35.20}=\dfrac{11.12.35.2.20.3}{12.35.20}=66\)
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5) 24*(15+49)+12*(50+42)
=24*64+12*92
=24*64+12*2*46
=24*64+24*46
=24*(64+46)
=24*110
=2640
45 x ( 13 + 78) + 9 x ( 87 + 22 ) x 5
= 45 x ( 13 + 78) + 45 x ( 87 + 22 )
= 45 x ( 13 + 78 + 87 + 22 )
= 45 x 200
= 9000
45 x ( 13 + 78) + 9 x ( 87 + 22 ) x 5
= 45 x 91 + 45 x 109
= 45 x ( 91 + 109 )
= 45 x 200
= 9000