Tính :
a)
b)
\(\displaystyle{4 \over {11}} + {5 \over {11}} \\\displaystyle{2 \over 3} + {4 \over 5} \\\displaystyle{5 \over 7} + {9 \over {14}} \\\displaystyle2 + {5 \over 8}\)
a)
b)
\(\displaystyle{4 \over {11}} + {5 \over {11}} = {9 \over {11}} \\\displaystyle{2 \over 3} + {4 \over 5} = {{10} \over {15}} + {{ 12} \over {15}} = {{22} \over {15}} \\\displaystyle{5 \over 7} + {9 \over {14}} = {{10} \over {14}} + {9 \over {14}}= {{19} \over {14}} \\\displaystyle 2 + {5 \over 8} ={{2} \over 1} + {5 \over 8}= {{16} \over 8} + {5 \over 8}= {{21} \over 8}\)
-- Mod Toán lớp 5