A photocopier can enlarge and reduce documents by a certain percentage. You accidentally enlarged a document by 20%. By what percent do you need to reduce this copy by to get the same size as the original?
*Give your answer to 2 decimal places. Include the % sign in your answer.

You are conducting a science experiment and have 180 ml of an 8% salt solution.
This means, in the 180 ml of water, there are 180 $\times$ 0.08 $=$ 14.4 g of salt in the 180 ml of water.

Your teacher asks you to make a 10% salt solution using 3 methods:

a) By evaporating water. How many ml of water would you need to evaporate?
b) By adding salt. How many grams of salt would you need to add? Assume 1 gram of salt adds 1 ml to the solution.
c) By adding a 15% salt solution. How many ml of this solution would you need to add?

There are 100 people in a room where exactly 99% are mathematicians. How many mathematicians must leave the room to bring down the percentage of mathematicians in the room to exactly 98%?

a) A store marks up an item by $20\%$ but it doesn’t sell so they mark this price down by $20\%$ and put it on sale. When the item was sold, the loss on this sale was $60$ yen. Find the original price of this item.
b) A store marks up an item by $25\%$ but it doesn’t sell so they mark this price down by $\fbox{___%}$ and put it on sale. When the item was sold, the percentage profit on this sale was $5\%$. Find the number that goes in the blank.
*a)You don’t need to include “yen” in your answer.

$25\%$ of $x\%$ of $x\%$ of $x$ is $\frac{729}{40}$. Find $x$.

A speaker talked for sixty minutes to a full auditorium. Twenty percent of the audience heard the entire talk and ten percent slept through the entire talk. Half of the remainder heard one-third of the talk and the other half heard two-thirds of the talk. What was the average number of minutes of the talk heard by members of the audience?

At a summer camp, $60\%$ of the children play soccer, $30\%$ of the children swim, and $40\%$ of the soccer players swim. What percent of the non-swimmers play soccer?
*Give your answer to one decimal place. Include the % sign in your answer.

$a=100$ rounded to $1$ significant figure,
$b=100$ rounded to the nearest ten and
$c=100$ rounded to the nearest integer.
Find the upper bound of $\frac{a+b}{b+c}\times\frac{c}{a}$.
*Give your answer correct to 3 decimal places.