百分數與變分

If $x:y=3:4$ and $2x+5y=598$, find $x$.

If $1$ Australian dollar is equivalent to $4.69$ H.K. dollars and $100$ Japanese yen are equivalent to $5.35$ H.K. dollars, how many Japanese yen are equivalent to $1$ Australian dollar? Give your answer correct to the nearest Japanese yen.

It is given that $y$ varies inversely as $x^3$. If $x$ is increased by $100\%$, then $y$ is

A man bought a box of $200$ apples for $\$500$. $10$ of the apples were rotten and the rest were sold at $\$4$ each. Find his percentage profit correct to 2 significant figures.

If $\dfrac{x+2y}{3x-4y}=5$, then $x:y=$

If $\dfrac{a}{b}=\dfrac{c}{d}$, which of the following must be true? I. $\dfrac{a}{c}=\dfrac{b}{d}$ II. $\dfrac{a+b}{b}=\dfrac{c+d}{d}$ III. $\dfrac{a-b}{b}=\dfrac{c-d}{d}$

If $x$ varies inversely as $y$ and directly as $z^2$, then

There are $1\,200$ students in a school, of which $640$ are boys and $560$ are girls. If $55\%$ of the boys and $40\%$ of the girls wear glasses, what percentage of students in the school wear glasses?

In a map of scale $1:500$, the length and breadth of a rectangular field are $2\text{ cm}$ and $3\text{ cm}$ respectively. Find the actual area of this field.

Find the interest on $\$10\,000$ at $16\%$ per annum for $2$ years, compounded half-yearly. Give the answer correct to the nearest dollar.