Đáp án + Giải thích các bước giải:
`A=4/7.31+6/7.41+9/10.41+7/10.57`
`=> A=[5.4]/[5(7.31)] + [5.6]/[5(7.41)]+[5.9]/[5(10.41)]+[5.17]/[5(10.57)]`
`=> A=\frac{20}{35.31}+\frac{30}{35.41}+\frac{45}{50.41}+\frac{35}{50.57}`
`=> A=5*(\frac{4}{35.31}+\frac{6}{35.41}+\frac{9}{50.41}+\frac{7}{50.57})`
`=> A=5*(\frac{1}{31}-\frac{1}{35}+\frac{1}{35}-\frac{1}{41}+\frac{1}{41}-\frac{1}{50}+\frac{1}{50}-\frac{1}{57})`
`=> A=5*(1/31-1/57)`
`=> A=5*26/1767`
`=> A=130/1767`
