( 273 + 439 ) - ( 439 - 125 - 2 )
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![](https://rs.olm.vn/images/avt/0.png?1311)
1) 18+14+16+35+110+160+150+145+158+140+55+25
= (14+16)+(35+25)+(145+55)+(140+160)+(158+18)+(110+150)
= 30+ 60 +200+ 300+ 176+ 260
= 590+ 436= 1026.
2) 62+ 78 +48+ 96+85+ 91
= (62 +48)+ (96 +85 +91+ 78)
= 110 + 350= 460.
3) 107 +439 + 666 +673+ 358 + 187
= (107 + 673) + ( 439 + 666) + ( 358+ 187)
= 780 + (1105 + 545)
= 780+ 1650= 2430.
4) 187 + 62+ 78+48+ 96+ 85+ 91+107+ 439+ 666+ 673+ 358
= (187 + 673) + ( 62+ 78)+ (439+ 91)+ ( 85+ 358+ 107)+ (666+ 96+ 48)
= (860+ 140)+ (530+ 550+ 810)
= 1000+ 1890= 2890.
![](https://rs.olm.vn/images/avt/0.png?1311)
Đáp án cần chọn là: B
4 15 − 2 65 − 4 39 = 52 195 − 6 195 − 20 195 = 52 − 6 − 20 195 = 26 195 = 2 15
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Lời giải:
a.
$23+23\times 45+23\times 44=23\times (1+45+44)=23\times 90$
$=23\times (100-10)=23\times 100-23\times 10=2300-230=2070$
b.
$=36\times 280-36\times 79-36$
$=36\times (280-79-1)=36\times (280-80)=36\times 200=7200$
c.
$=72\times 10+72\times 25+72\times 66-72$
$=72\times (10+25+66-1)=72\times 100=7200$
![](https://rs.olm.vn/images/avt/0.png?1311)
\(4^{39}+4^{40}+4^{41}=4^{38}.\left(4+4^2+4^3\right)=4^{38}.84⋮28\left(Vì:84⋮28\right)\)
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![](https://rs.olm.vn/images/avt/0.png?1311)
`@` `\text {Ans}`
`\downarrow`
`23 + 23 \times 45 + 23 \times 44`
`= 23 \times (1+45 + 44)`
`= 23 \times 90`
`= 2070`
`b)`
`36 \times 280 - 9 \times 79 \times 4 - 36`
`= 36 \times 280 - 9 \times 4 \times 79 - 36`
`= 36 \times 280 - 36 \times 79 - 36`
`= 36 \times (280 - 79 - 1)`
`= 36 \times 200`
`= 7200`
`c)`
`8 \times 9 \times 10 + 6 \times 25 \times 12 + 4 \times 18 \times 66 - 2 \times 36`
`= 2 \times 4 \times 9 \times 10 + 6 \times 2 \times 6 \times 25 + 2 \times 2 \times 18 \times 66 - 2 \times 36`
`= 10 \times 2 \times 36 + 36 \times 2 \times 25 + 36 \times 2 \times 66 - 2 \times 36`
`= 36 \times 2 \times (10 + 25 + 66 - 1)`
`= 72 \times 100`
`= 7200`
_____
`c)`
`439 \times 78 - 38 \times 78 - 78`
`= 78 \times (439 - 38 - 1)`
`= 78 \times 400`
`= 31200`
`d)`
`24 \times 13 + 6 \times 89 \times 4 - 2 \times 24`
`= 24 \times 13 + 24 \times 89 - 2 \times 24`
`= 24 \times (13 + 89 - 2)`
`= 24 \times 100`
`= 2400`
![](https://rs.olm.vn/images/avt/0.png?1311)
x * 3561 + 439 * x = 28000
x * ( 3561 + 439 ) = 28000
x * 4000 = 28000
x = 28000 : 4000 = 7
dấu * là dấu nhân bạn nhé
x *3561 + 439 *x=28000
x * (3561+439)=28000
x * 4000 =28000
x =28000:4000
x = 7
(273+439)-(439-125-2)
= 712-312
=400
(273+439)-(439-125-2)
=712-312
=400
Học giỏi nha bạn !