1988 年

$y$ varies inversely as $x^2$. If $x$ is increased by $100\%$, then $y$ is

$8abc^3$ is the H.C.F. of $24ab^2c^3$ and

$X$ sells an article to $Y$ at a profit. $Y$ then sells it to $Z$ for $\$60$ at a profit of $20\%$. If $X$ had sold the article directly to $Z$ for $\$60$, how much MORE profit would he have made?

A car travels from $P$ to $Q$. If its speed is increased by $k\%$, then the time it takes to travel the same distance is reduced by

A bag contains $n$ balls of which $60\%$ are red and $40\%$ are white. After 10 red balls are taken out from the bag, the percentage of red balls becomes $50\%$. Find $n$.

The weight of a gold coin of a given thickness varies as the square of its diameter. If the weights of two such coins are in the ratio $1:4$, then their diameters are in ratio

A cylindrical hole of radius $r$ is drilled through a solid cylinder, base radius $2r$ and height $r$, as shown in the figure. The percentage increase in the total surface area is

The figure shows the circumscribed circle $P$ and the inscribed circle $Q$ of the square $ABCD$. Find area of $P$ : area of $Q$.

If $x$ and $y$ can take any value between $0$ and $360$, what is the greatest value of $2\sin x^\circ-\cos y^\circ$?

The figure shows the graph of the function