Pre Algebra: Proportions

1. If $\dfrac{x}{16}=\dfrac{12}{y}$, then what is the value of $xy$?

(A) $\dfrac{3}{4}$
(B) $144$
(C) $192$
(D) $\dfrac{4}{3}$
(E) $224$

2. If $\dfrac{a}{8}=\dfrac{1}{16}$, then what is the value of $a$?

(A) $\dfrac{1}{2}$
(B) $128$
(C) $8$
(D) $16$
(E) $2$

3. If $\dfrac{12}{n-2}=\dfrac{8}{2n}$, then what is the value of $n$?

(A) $-1$
(B) $1$
(C) $\dfrac{1}{2}$
(D) $\dfrac{-1}{2}$
(E) $-2$

4. The ratio of 1.8 to 3 is not equal to which of the following ratios?

(A) 18 to 30
(B) 3 to 10
(C) 6 to 10
(D) 9 to 15
(E) 0.6 to 1