1981 年

The marked price of a book is $\$x$. $30\%$ of this price is profit. If the book is sold at a discount of $20\%$, what will the profit then be?

A group consists of $n$ boys and $n$ girls. If two of the girls are exceeded by two other boys, then $51\%$ of the group members will be boys. What is $n$?

If the surface area of a spherical soap bubble increases by $44\%$, its volume increases by

The total area of the six faces of the solid cube in the figure is $96\text{ cm}^2$. What is the length of the diagonal $AB$?

A merchant sold $100$ chairs. $80$ of them were sold at a profit of $30\%$ on each chair, while $20$ of them were sold at a loss of $40\%$ on each chair. What is his percentage gain or loss on the whole stock?

If $0^\circ<\theta<90^\circ$ and $\sin\theta=\dfrac{k}{2}$, then $\cos\theta=$

$\tan\theta\sin\theta-\dfrac{1}{\cos\theta}=$

If $0^\circ\le\theta\le360^\circ$, the number of roots of the equation $2\sin\theta\cos\theta-\cos\theta=0$ is

An angle measures $x$ radians. What is its measure in degrees?

In the figure, $\cos\theta=$