Tính bằng phương pháp hợp lí: a) 11 1/4 - (2 5/7 + 5 1/4) b) (8 5/11 + 3 5/8)

* Hướng dẫn giải

a) $11\frac{1}{4}-\left(2\frac{5}{7}+5\frac{1}{4}\right)=11\frac{1}{4}-2\frac{5}{7}-5\frac{1}{4}$$=\left(11\frac{1}{4}-5\frac{1}{4}\right)-2\frac{5}{7}=6-2\frac{5}{7}=5\frac{7}{7}-2\frac{5}{7}=3\frac{2}{7}$

b) $\left(8\frac{5}{11}+3\frac{5}{8}\right)-3\frac{5}{11}=8\frac{5}{11}+3\frac{5}{8}-3\frac{5}{11}$$=\left(8\frac{5}{11}-3\frac{5}{11}\right)+3\frac{5}{8}=5+3\frac{5}{8}=8\frac{5}{8}$