Question

Bài 1: Rút gọn rồi tính :

a) \(\frac{2}{5}+\frac{9}{15}\)                     b) \(\frac{15}{45}+\frac{25}{30}\)                            c) \(\frac{28}{32}+\frac{45}{72}\)                         d) \(\frac{4}{8}+\frac{8}{24}\)

Bài 3 : Tính :

a) \(\frac{2}{5}+\frac{2}{3}+\frac{3}{4}\)                                        b) \(\frac{1}{3}+\frac{5}{12}+\frac{5}{6}\)                            c) \(\frac{1}{6}+\frac{5}{24}+\frac{2}{3}\)                       

 

Answer 1

B3

a)\(\frac{2}{5}+\frac{2}{3}+\frac{3}{4}=\frac{24}{60}+\frac{40}{60}+\frac{45}{60}\)\(=\frac{109}{60}\)

b)\(\frac{1}{3}+\frac{5}{12}+\frac{5}{6}=\frac{4}{12}+\frac{5}{12}+\frac{10}{12}\)\(=\frac{19}{12}\)

c)\(\frac{1}{6}+\frac{5}{24}+\frac{2}{3}=\frac{4}{24}+\frac{5}{24}+\frac{16}{24}\)\(=\frac{25}{24}\)

Answer 2

\(\frac{2}{5}+\frac{9}{15}\)

\(=\frac{2}{5}+\frac{3}{5}\)

\(=\frac{2+3}{5}\)

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

\(=1\)

Answer 3

B1

a)\(\frac{2}{5}+\frac{9}{15}=\frac{2}{5}+\frac{3}{5}=\frac{5}{5}=1\)                                     c)\(\frac{28}{32}+\frac{45}{72}=\frac{7}{8}+\frac{5}{8}=\frac{12}{8}=\frac{3}{2}\)

b)\(\frac{15}{45}+\frac{25}{30}=\frac{1}{3}+\frac{5}{6}=\frac{2}{6}+\frac{5}{6}=\frac{7}{6}\)                   d)\(\frac{4}{8}+\frac{8}{24}=\frac{1}{2}+\frac{1}{3}=\frac{3}{6}+\frac{2}{6}=\frac{5}{6}\)

Answer 4

\(\frac{2}{5}+\frac{9}{15}=\frac{2}{5}+\frac{3}{5}=\frac{2+3}{5}=\frac{5}{5}=1\)