Ta có : \(A=\frac{40}{31.39}+\frac{35}{39.46}+\frac{30}{46.52}+\frac{25}{52.57}=5\left(\frac{8}{31.39}+\frac{7}{39.46}+\frac{6}{46.52}+\frac{5}{52.57}\right)\)

\(=5\left(\frac{1}{31}-\frac{1}{39}+\frac{1}{39}-\frac{1}{46}+\frac{1}{46}-\frac{1}{52}+\frac{1}{52}-\frac{1}{57}\right)=5\left(\frac{1}{31}-\frac{1}{57}\right)=5.\frac{26}{1767}=\frac{130}{1767}\)

Đăt \(A=\dfrac{40}{31.39}+\dfrac{35}{39.46}+\dfrac{30}{46.52}+\dfrac{25}{52.57}+\dfrac{20}{57.61}\)

\(\Leftrightarrow A=5.\left(\dfrac{8}{31.39}+\dfrac{7}{39.46}+\dfrac{6}{46.52}+\dfrac{5}{52.57}+\dfrac{4}{57.61}\right)\)

\(\Leftrightarrow A=5.\left(\dfrac{1}{31}-\dfrac{1}{39}+\dfrac{1}{39}-\dfrac{1}{46}+\dfrac{1}{46}-\dfrac{1}{52}+\dfrac{1}{52}-\dfrac{1}{57}+\dfrac{1}{57}-\dfrac{1}{61}\right)\)\(\Leftrightarrow A=5.\left(\dfrac{1}{31}-\dfrac{1}{61}\right)\)

\(\Leftrightarrow A=5.\dfrac{30}{31.61}\)

\(\Leftrightarrow A=\dfrac{150}{1891}\)

\(A=5\left(\frac{8}{31.39}+\frac{7}{39.46}+\frac{6}{46.52}+\frac{5}{52.57}\right)=8\left(\frac{1}{31}-\frac{1}{39}+\frac{1}{39}-\frac{1}{46}+\frac{1}{46}-\frac{1}{52}+\frac{1}{52}-\frac{1}{57}\right)\)=\(8\left(\frac{1}{31}-\frac{1}{57}\right)=8\left(\frac{26}{1767}\right)=\frac{208}{1767}\)

208/1767

tich tớ nhé Nguyễn Trọng Đức Siu Đệp Choai

ket qua = 208/1767 ban nha

222222222222222222222222222222

\(A=\frac{40}{31}-\frac{40}{39}+\frac{35}{39}-\frac{35}{46}+\frac{30}{46}-\frac{30}{52}+\frac{25}{52}-\frac{25}{57}\)

\(A=\frac{1}{31}-\frac{1}{39}+\frac{1}{39}-\frac{1}{46}+\frac{1}{46}-\frac{1}{52}+\frac{1}{52}-\frac{1}{57}\)

\(A=\frac{1}{31}-\frac{1}{57}\)

tiếp theo tính A và B tương tự rồi tìm tỉ số, ta lấy A:B*100=?%

haizzz ghi đề lại đàng hoàng đi cha nội ơi

duyệt giùm đê