`#ChieyewCucCuk `
`1. ` Tính`: `
`a)2/3+3/5 `
`=10/15+9/15 `
`=19/15 `
`------ `
`7/12-2/7+1/12 `
`=25/84+1/12 `
`=8/21 `
`------ `
`12/17-5/17-4/17 `
`=12-5-4/17 `
`=3/17 `
`------ `
`b)578,69+281,78 ` `594,72+406,36-329,47 `
`=860,47 ` `=1001,08-329,47 `
`=671,61 `
`2. ` Tính bằng cách thuận tiện nhất`: `
`a)7/11+3/4+4/11+1/4 `
`=(7/11+4/11)+(3/4+1/4) `
`= 1 + 1 `
`=2 `
`------ `
`b)72/99-28/99-14/99 `
`=(72/99-28/99)-14/99 `
`=44/99-14/99 `
`=30/99 `
`=10/33 `
`------ `
`c)69,78+35,97+30,22 `
`=(69,78+30,22)+35,97 `
`=100+35,97 `
`=135,97 `
`------ `
`d)83,45-30,98-42,47 `
`83,45-(30,98+42,47) `
`=83,45-73,45 `
`=10 `