Question

daca numerele rationale pozitive a si b verifica a/2=5/b calculati ​

Answer 1

$\it \dfrac{a}{2}=\dfrac{5}{b} \Rightarrow a\cdot b=2\cdot5 \Rightarrow a\cdot b=10\\ \\ \\ a)\ \ 30-2\cdot a\cdot b=30-2\cdot10=30-20=10\\ \\ b)\ \ \dfrac{a\cdot b-10}{21}=\dfrac{10-10}{21}=\dfrac{0}{21}=21\\ \\ \\ c)\ \ 11-a\cdot b=11-10=1\\ \\ \\ \dfrac{27\cdot a\cdot b}{30}=\dfrac{27\cdot10}{30}=\dfrac{270}{30}=9$