百分數與變分

A sum of $\$30\,000$ is deposited at an interest rate of $5\%$ per annum for $2$ years, compounded yearly. Find the interest correct to the nearest dollar.

The scale of a map is $1:5000$. If the area of a garden on the map is $4\text{ cm}^2$, then the actual area of the garden is

It is given that $y$ is partly constant and partly varies inversely as $x$. When $x=1$, $y=-1$ and when $x=2$, $y=1$. Find the value of $x$ when $y=2$.

The marked price of a bag is $\$900$. If the bag is sold at the marked price, then the percentage profit is $50\%$. If the bag is sold at a $20\%$ discount on the marked price, then the profit is

The costs of rice of brand $A$ and rice of brand $B$ are $\$8/\mathrm{kg}$ and $\$4/\mathrm{kg}$ respectively. If $x\ \mathrm{kg}$ of rice of brand $A$ and $y\ \mathrm{kg}$ of rice of brand $B$ are mixed so that the cost of the mixture is $\$5/\mathrm{kg}$, find $x:y$.

Suppose that $y$ varies directly as $x$ and inversely as $z^2$. If $x$ and $z$ are both decreased by $20\%$, then $y$

It is known that $\mathrm{f}(x)$ varies partly as $x$ and partly as $x^2$. If $\mathrm{f}(1)=5$ and $\mathrm{f}(2)=16$, then $\mathrm{f}(3)=$

If the bus fare is increased from $\$4$ to $\$5$, then the percentage increase of the fare is

A sum of $\$30\,000$ is deposited at an interest rate of $12\%$ per annum for $4$ years, compounded monthly. Find the amount correct to the nearest dollar.

Let $a$ and $b$ be non-zero numbers. If $7a+5b=3a+8b$, then $a:b=$