1980 年

In the figure, $ABCDE$ is a regular pentagon. $\angle ADB=$

In the figure, $ABCD$ is a square and $ABE$ is an equilateral triangle. $\angle ADE=$?

In the figure, the two circles intersect at $A$ and $B$. $CAE$ and $CBD$ are straight lines. $\angle CED=$

In the figure, circle $AXB$ passes through the centre of circle $AYB$. $y=$

In the figure, $ABCD$ is a rectangle. $\angle BEF=90^\circ$. Which two of the triangles I, II, III and IV must be similar?

In the figure, the inscribed circle of $\triangle ABC$ touches $AC$ at $D$. If $AB=7$, $AC=5$ and $AD=2$, then $BC=$

A certain sum of money is just sufficient to pay the wages of one man for $m$ days or the wages of one boy for $n$ days. For how many days will this sum be just sufficient to pay the wages of one man and one boy together?

If the value of $y^2+3y+7$ is $2$, what is the value of $2y^2+6y-3$?

$A$, $B$, $C$ are three spheres. If $\dfrac{\text{Surface area of }A}{\text{Surface area of }B}=4$ and $\dfrac{\text{Volume of }B}{\text{Volume of }C}=2$, then $\dfrac{\text{Volume of }A}{\text{Volume of }C}=$

The $2n^{\text{th}}$ term of the geometric progression $8,-4,2,-1,\ldots$ is