Giải bài tập 1 trang 153 sgk toán 4

a) $\frac{3}{5}+ \frac{11}{20}= \frac{12}{20}+ \frac{11}{20}= \frac{12+11}{20}= \frac{23}{20}$

b) $\frac{5}{8}- \frac{4}{9}= \frac{45}{72}-\frac{32}{72}= \frac{45-32}{72}= \frac{13}{72}$

c) $\frac{9}{16}\times \frac{4}{3}=\frac{9\times 4}{16\times 3}=\frac{36}{48}=\frac{3}{4}$

d) $\frac{4}{7}\div \frac{8}{11}=\frac{4\times 11}{7\times 8}=\frac{44}{56}=\frac{11}{14}$

e) $\frac{3}{5}+\frac{4}{5}\div \frac{2}{5}= \frac{3}{5}+ \frac{4\times 5}{5\times 2}= \frac{3}{5}+\frac{20}{10}=\frac{6}{10}+\frac{20}{10}=\frac{26}{10}=\frac{13}{5}$