When a quantity grows (gets bigger), then we can compute its PERCENT INCREASE.
When a quantity shrinks (gets smaller), then we can compute its PERCENT DECREASE.
These concepts are thoroughly explored on this page.
Percent Increase
When a quantity grows (gets bigger), then we can compute its PERCENT INCREASE:
$\text{PERCENT INCREASE} =
\frac{\displaystyle{(\text{new amount}  \text{original amount})}}
{\displaystyle\text{original amount}}
$
Some people write this formula with $\,100\%\,$ at the end, to emphasize that since it is percent increase, it should be reported as a percent. So, here's an alternate way to give the formula:
$\text{PERCENT INCREASE} =
\frac{\displaystyle{(\text{new amount}  \text{original amount})}}
{\displaystyle\text{original amount}}\cdot 100\%
$
Recall that $\,100\% = 100\cdot\frac{1}{100} = 1\,$. So, $\,100\%\,$ is just the number $\,1\,$! Multiplying by $\,1\,$ doesn't change anything except the name of the number! (See examples below.) By the way, there's a very optimistic percent Tshirt here. Wear it and watch people smile! 
Visualizing Percent Increase
NOTE:
If $\,\text{percent increase} = 75\%\,$, then the formula
$$\text{percent increase} =
\frac{\displaystyle{(\text{new}  \text{original})}}
{\displaystyle\text{original}}
$$
becomes
$$75\% =
\frac{\displaystyle{(\text{new}  \text{original})}}
{\displaystyle\text{original}}
$$
and solving for ‘new’ gives:
$$
\text{new} = \text{original} + 75\%(\text{original})
$$

CONCEPT QUESTIONS EXERCISE:
On this exercise, you will not key in your answer.However, you can check to see if your answer is correct. 
PROBLEM TYPES:
