Tính (theo mẫu):
Mẫu: \(\displaystyle {9 \over {10}} \times {5 \over 6} = {{9 \times 5} \over {10 \times 6}} = {{3 \times \not 3 \times \not 5} \over {\not5 \times 2 \times \not 3 \times 2}} \displaystyle = {3 \over 4}\)
a) \(\displaystyle {9 \over {22}} \times {{33} \over {18}} =\; .........\)
b) \(\displaystyle {{12} \over {35}}:{{36} \over {25}} =\; ..........\)
c) \(\displaystyle {{19} \over {17}}:{{76} \over {51}} = \;..........\)
a) \(\displaystyle {9 \over {22}} \times {{33} \over {18}} = {{9 \times 33} \over {22 \times 18}} \displaystyle = {{\not 9 \times \not 11 \times 3} \over {\not11 \times 2 \times \not9 \times 2}} = {3 \over 4}\)
b) \(\displaystyle {{12} \over {35}}:{{36} \over {25}} = {{12} \over {35}} \times {{25} \over {36}} = {{12 \times 25} \over {35 \times 36}} \) \(\displaystyle = {{\not6 \times \not2 \times \not5 \times 5} \over {7 \times \not5 \times \not6 \times 3 \times \not2}} = {5 \over {21}}\)
c) \(\displaystyle {{19} \over {17}}:{{76} \over {51}} = {{19} \over {17}} \times {{51} \over {76}} \) \(\displaystyle = {{\not19 \times \not17 \times 3} \over {\not17 \times \not19 \times 4}} = {3 \over {4}}\)
-- Mod Toán lớp 5
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