\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}\)

\(=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}\)

\(=1-\frac{1}{5}\)

\(=\frac{4}{5}\)

\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{9900}\)

\(=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{98.99}+\frac{1}{99.100}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+....+\frac{1}{98}-\frac{1}{99}+\frac{1}{99}-\frac{1}{100}+\frac{1}{100}\)

\(=1-\frac{1}{100}\)

\(=\frac{99}{100}\)

Từng ý một nhanh hơn nhá

kb nhé

1994*867+1994*133

=1994*(867+133)

=1994*1000

=1994000

: D: 1994*867+1995*133=39890000

328450-296+72296-450+600000

=(328450-450)+(72296-296)+600000

=328000+72000+600000

=400000+600000

=1000000

= (328450 - 450) + (72296 - 296 + 600000)

= 328000 + 72000 + 600000

= 400000 + 600000

= 1000000

\(\frac{14}{15}\div\frac{7}{20}=\frac{14}{15}\times\frac{20}{7}=\frac{14\times20}{15\times7}=\frac{8}{3}\)

\(\frac{9}{8}\div\frac{27}{16}=\frac{9}{8}\times\frac{16}{27}=\frac{9\times16}{8\times27}=\frac{2}{3}\)

kết quả của mik bằng 127^,812 nhé.

Chúc Bạn Học Giỏi

127812 nha

35 x 12 + 23 x 24 + 19 x 12

= 35 x 12 + 23 x 12 x 2 + 19 x 12

= 12 x (35 + 23 x 2 + 19)

= 12 x 100

= 1200