Giải bài 5 trang 118 - SGK Toán 4
Tính (theo mẫu):
a) \(\dfrac{15\,\times\,7}{30\,\times\,11};\) b) \(\dfrac{4\,\times\,5\,\times\,6}{12\,\times\,15\,\times\,9};\) c) \(\dfrac{6\,\times\,8\,\times\,11}{33\,\times\,16}.\)
Mẫu: \(\dfrac{15\,\times\,7}{30\,\times\,11} = \dfrac {\cancel{15} \times {7} } {\cancel{15} \times {2} \times {11}}=\dfrac{7}{22} \)
Tính:
b) \(\dfrac{4\,\times\,5\,\times\,6}{12\,\times\,15\,\times\,9}=\dfrac {\cancel{4} \times \cancel{5} \times {6}} {\cancel{12} \times \cancel{15} \times {9}}=\dfrac{1\,\times\,1\,\times\,6}{3\,\times\,3\,\times\,9}=\dfrac {{1} \times {1} \times \cancel{6}} {\cancel{3} \times {3} \times {9}}=\dfrac{2}{27} \)
c) \(\dfrac{6\,\times\,8\,\times\,11}{33\,\times\,16} = \dfrac{2\times3\,\times\,8\,\times\,11}{11\times3\,\times\,16}=\dfrac {{2} \times \cancel{3}\times \cancel{8} \times\cancel {11}} {\cancel{11} \times \cancel{3} \times \cancel{16}}=\dfrac{2}{2}=1\)
