\(a,=\dfrac{1\times4}{12\times5}=\dfrac{1}{15}\\ --------\\ b,=\dfrac{40\times21}{7\times5}=24\\ --------\\ c,=\dfrac{9}{5}\times\dfrac{7}{4}=\dfrac{63}{20}\\ --------\\ d,=\dfrac{11}{24}\times\dfrac{3}{44}=\dfrac{1}{32}\)
`1 / 12 xx 4/5 = 4/60 = 1/15`
`40/7 xx 21/5 = `\(\dfrac{5\times8\times3\times7}{7\times5}=\dfrac{24}{1}=24\)
`9/5 : 4/7 = 9/5 xx 7/4 = 63/20`
`11/24 : 44/3 = 11/24 xx 3/44 = 33/1056= 1/32`
\(\dfrac{1}{12}.\dfrac{4}{5}=\dfrac{4}{60}=\dfrac{4:4}{60:4}=\dfrac{1}{15}\)
\(\dfrac{40}{7}.\dfrac{21}{5}=\dfrac{840}{35}=24\)
\(\dfrac{9}{5}:\dfrac{4}{7}=\dfrac{9}{5}.\dfrac{7}{4}=\dfrac{63}{20}\)
\(\dfrac{11}{24}:\dfrac{44}{3}=\dfrac{11}{24}.\dfrac{3}{44}=\dfrac{33}{1056}=\dfrac{33:33}{1056:33}=\dfrac{1}{32}\)