[tex](1)\\R\cdot I=a\ \ \ \ and\ \ \ 50\cdot 0.15=a\\\\ \ \Rightarrow\ \ \ a=7.5\ \ \ \Rightarrow\ \ I= \frac{7.5}{R} \ \ \ \Rightarrow\ \ \ Ans.\ A.\\\\(2)\\x\cdot y=a\ \ \ and\ \ \ 8\cdot6=a\\\\ \ \Rightarrow\ \ \ a=48\ \Rightarrow\ \ \ xy=48\ \ \ \Rightarrow\ \ \ 10y=48\ \Rightarrow\ \ \ y=4.8\ \Rightarrow\ \ \ Ans.\ D.\\\\(3)\\xy=-12\ \ \Rightarrow\ \ \ constant=-12\ \ \Rightarrow\ \ \ Ans.\ D.\\\\[/tex]
[tex](4)\\xy=-12\\\\e.g.:\ \ \ x=3\ \ and\ \ y=-4\ \ \ \ or\ \ \ \ x=-3\ \ and\ \ y=4\ \ \Rightarrow\ \ Ans.\ A.\\\\(5)\\V\cdot T=a\ \ \ and\ \ \ 18\cdot 3=a\\\\ \ \ \Rightarrow\ \ \ a=54\ \ \ \Rightarrow\ \ \ V\cdot T=54\ \ \ \Rightarrow\ \ \ V= \frac{54}{T} \ \ \ \Rightarrow\ \ \ Ans.\ C.[/tex]
