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Found problems: 2

2007 National Chemistry Olympiad, 42
Tags: direct proportion
The mass of metal deposited by the electrolysis of an aqueous solution of metal ions increases in direct proportion to which property? $\text{I. electrolysis current}$ $\text{II. electrolysis time}$ $\text{III. metal ion charge}$ $ \textbf{(A)}\ \text{I only} \qquad\textbf{(B)}\ \text{III only} \qquad\textbf{(C)}\ \text{I and II only} \qquad\textbf{(D)}\ \text{I, II, and III}\qquad$

1959 AMC 12/AHSME, 20
Tags: algebra , direct proportion , inversely proportional
It is given that $x$ varies directly as $y$ and inversely as the square of $z$, and that $x=10$ when $y=4$ and $z=14$. Then, when $y=16$ and $z=7$, $x$ equals: $ \textbf{(A)}\ 180\qquad\textbf{(B)}\ 160\qquad\textbf{(C)}\ 154\qquad\textbf{(D)}\ 140\qquad\textbf{(E)}\ 120 $