Tính bằng cách thuận tiện nhất:
42*40 + 6*8*21 - 22*96=?
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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
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
53x39+47x39-53x21-47x21
=39x ( 53+47) - 21x(53+47)
=39 x100 - 21x100
= 100x(39-21)
=100x18
=1800
2x53x12 +4x6x87 - 3x8x40
= (2x12)x53 + (4x16)x87 - (3x8) x40
= 24x53 + 24x87 + 24x40
= 24( 53+87+40)
= 24x180
=4320
1.
a) 25.5.4.27
= ( 25 . 4 ).( 5 . 2 ).27
= 100 . 10 . 27
= 27000
b) 28 . 64 + 28 . 36
= 28 . ( 64 + 36 )
= 28 . 100
= 2800
2.
a) 135 + 360 + 65 + 40
= ( 135 + 65 ) + ( 360 + 40 )
= 200 + 400 = 600
b) 463 + 318 + 127 + 22
= ( 463 + 127 ) + ( 318 + 22 )
= 590 + 340
= 930
c) 20 + 21 + 22 +... + 29 + 30
= ( 20 + 30 ) + ( 21 + 29 ) + ( 22 + 28 ) + ( 23 + 27 ) + ( 24 + 26 ) + 25
= 50 . 5 + 25
= 250 + 25
= 175
3.
a) 14 . 50 ; 16.25
= ( 14 : 2 ) . ( 50 . 2 ) = ( 16 : 4 ) . ( 25 . 4 )
= 7 . 100 = 4 . 100
= 700 = 400
b)
2100 + 50
= ( 2100 . 2 ) : ( 50 . 2 )
= 4200 : 100
= 42
1400 : 25
= ( 1400 . 4 ) : ( 25 . 4 )
= 5600 : 100
= 56
c)
132 : 12
= ( 120 + 12 ) : 12
= 120 : 12 + 12 : 12
= 10 + 1
= 11
96 : 8
= ( 80 + 16 ) : 8
= 80 : 8 + 16 : 8
= 10 + 2
= 12
tk mik nha
1.
a) 25.5.4.27.2=(25.4).(5.2).27=100.10.27=27000
b) 28.64+28.36=28.(64+36)=28.100=2800
2.
a) 135+360+65+40= (135+65)+(360+40)=200+400=600
b) 463+318+127+22=(463+127)+(318+22)=590+340=930
c) 20+21+22+...+29+30=(20+30)+(21+29)+(22+28)+(23+27)+(24+26)+25=50+50+50+50+50+25=50.5+25= 275
3.
a) 14.50=7.2.5.10=(7.10).(2.5)=70.10=700
16.25=4.4.25=4.100=400
b) \(2100\div50=\left(2000+100\right)\div50\)
\(=2000\div50+100\div50=40+2=42\)
\(1400\div25=\left(1000+400\right)\div25\)
\(=1000\div25+400\div25=40+16=56\)
c) \(132\div12=\left(144-12\right)\div12\)
\(=144\div12-12\div12=12-1=11\)
\(96\div8=\left(80+16\right)\div8\)
\(=80\div8+16\div8=10+2=12\)
10.20 phút, mỏi tay quá! Buồn ngủ quá!
\(=\dfrac{21}{11}\cdot\dfrac{22}{17}\cdot\dfrac{34}{42}=\dfrac{1}{2}\cdot2\cdot2=2\)
\(42\cdot40+6\cdot8\cdot21-22\cdot96\)
\(=42\cdot40+24\cdot42-22\cdot96\)
\(=42\left(40+24\right)-22\cdot1,5\cdot64\)
\(=64\cdot42-64\cdot33=64\cdot9=576\)