百分數與變分

A sum of $\$15\,000$ is deposited at an interest rate of $6\%$ per annum for $10$ years, compounded monthly. Find the interest correct to the nearest dollar.

The length of a rectangle is decreased by $20\%$ but its breadth is increased by $k\%$. If the area of the rectangle remains unchanged, find the value of $k$.

Let $m$ and $n$ be non-zero numbers. If $\dfrac{2m-n}{m-2n}=3$, then $m:n=$

It is given that $a$ varies directly as $b$ and inversely as $c^2$. When $b=6$ and $c=3$, $a=-2$. When $a=-9$ and $c=4$, $b=$

If the price of a magazine is $60\%$ higher than the price of a newspaper, then the price of the newspaper is

A sum of $\$40\,000$ is deposited at an interest rate of $4\%$ per annum for $3$ years, compounded quarterly. Find the amount correct to the nearest dollar.

If tea of brand $A$ costs $\$80/\text{kg}$ and tea of brand $B$ costs $\$40/\text{kg}$, then a mixture of $4\ \text{kg}$ of tea of brand $A$ and $6\ \text{kg}$ of tea of brand $B$ costs

It is given that $z$ varies directly as $x$ and directly as $y^2$. If $x$ is decreased by $20\%$ and $y$ is increased by $15\%$, then $z$

In a school, $55\%$ of the students are boys. It is given that $60\%$ of the boys and $30\%$ of the girls live in Kowloon. Find the probability that a randomly selected student from the school is a girl who lives in Kowloon.

If a dictionary is sold at its marked price, then the percentage profit is $30\%$. If the dictionary is sold at a $20\%$ discount on its marked price, then the profit is $\$5$. Find the cost of the dictionary.