Question

3. Tính rồi rút gọn :

a. 2/5 + 3/4               5/8 + 7/2                     4/9 +5/18            5/8 + 9/16

b. 9/5 - 5/9                12/7 -17/2                    11/8 - 8/11             17/6 - 6/17

Answer 1

\(a,\frac{2}{5}+\frac{3}{4}=\frac{8}{20}+\frac{15}{20}=\frac{23}{20}\)

\(\frac{5}{8}+\frac{7}{2}=\frac{5}{8}+\frac{28}{8}=\frac{33}{8}\)

\(\frac{4}{9}+\frac{5}{18}=\frac{8}{18}+\frac{5}{18}=\frac{13}{18}\)

\(\frac{5}{8}+\frac{9}{16}=\frac{10}{16}+\frac{9}{16}=\frac{19}{16}\)

\(b,\frac{9}{5}-\frac{5}{9}=\frac{81}{45}-\frac{25}{45}=\frac{56}{45}\)

\(\frac{12}{7}-\frac{17}{2}=\frac{24}{14}-\frac{119}{14}=-\frac{95}{14}\)

\(\frac{11}{8}-\frac{8}{11}=\frac{121}{88}-\frac{64}{88}=\frac{57}{88}\)

\(\frac{17}{6}-\frac{6}{17}=\frac{289}{102}-\frac{36}{102}=\frac{253}{102}\)

Answer 2

a. 2/5 + 3/4 = 8/20 + 15/20 = 23/20

5/8 + 7/2 = 5/8 + 28/8 = 33/8

4/9 + 5/18 = 8/18 + 5/18 = 13/18

5/8 + 9/16 = 10/16 + 9/16 = 19/16

b. 9/5 - 5/9 = 56/45 

12/7 - 17/2 = -95/14

11/8 - 8/11 = 57/88

17/6 - 6/17 = 253/102

Answer 3

a) \(\frac{2}{5}+\frac{3}{4}=\frac{8}{20}+\frac{15}{20}=\frac{23}{20}\)

\(\frac{5}{8}+\frac{7}{2}=\frac{5}{8}+\frac{28}{8}=\frac{33}{8}\)

\(\frac{4}{9}+\frac{5}{18}=\frac{8}{18}+\frac{5}{18}=\frac{13}{18}\)

\(\frac{5}{8}+\frac{9}{16}=\frac{10}{16}+\frac{9}{16}=\frac{19}{16}\)

b) \(\frac{9}{5}-\frac{5}{9}=\frac{81}{45}-\frac{35}{45}=\frac{46}{45}\)

\(\frac{12}{7}-\frac{17}{2}=\frac{24}{14}-\frac{119}{14}=-\frac{95}{14}\)

\(\frac{11}{8}-\frac{8}{11}=\frac{121}{88}-\frac{64}{88}=\frac{57}{88}\)

\(\frac{17}{6}-\frac{6}{17}=\frac{289}{102}-\frac{36}{102}=\frac{253}{102}\)