giúp mình với mình cần gấp

`a) 5800 + 200 + 2000 + 800`

`= (5800+2000) + (200+800)`

`=7800 + 1000`

`= 8800`

 ` `

`b) 17 xx (730 + 270)`

`= 17xx 1000 `

`= 17000`

` `

`25 xx 9 xx 4 xx 7`

`= (25xx4) xx ( 9 xx 7) `

`= 100 xx 63`

`= 6300`

 ` `

`831 xx 56 -831 xx 46`

`= 831 xx ( 56-46 )`

`= 831 xx 10`

`= 8310`

` ` 

`15/60 = (15:15)/(60:15) = 1/4`

`3/8 = 3/8`

`5/20= (5:5)/(20:5) = 1/4`

`15/40= (15:5)/(40:5) = 3/8`

`30/80 = (30:10)/(80:10) = 3/8`

Vậy phân số bằng nhau là: `15/60 =5/20`

và ` 3/8= 15/40= 30/80 `

`a)`

`5800+200+2000+800`

`=(200+800)+(5800+2000)`

`=1000+7800`

`=8800`

`b)`

`17×(730+270)`

`=17×1000`

`=17000`

`c)`

`25×9×4×7`

`=25×4×9×7`

`=100×63`

`=6300`

`d)`

`831×56-831×46`

`=831×(56-46)`

`=831×10`

`=8310`

`4`

`30/80=15/40=3/8=3/8`

Vậy `30/80=15/40=3/8`

`15/60=5/20=1/4`

Vậy `15/60=5/20`

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