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How to find percent of increase when do not know percentage?

I would like to know how to find the percent of increase when the percentage is unknown.

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Parviz F. | Mathematics professor at Community CollegesMathematics professor at Community Colle...
4.8 4.8 (4 lesson ratings) (4)
The notion of percentage creates a great deal of episode among students. The reason for that is, because focus hinges on procedure of, how to do this and that, without paying attention to what it is?
  Percentage is simply a ratio, and ratio is a fraction, is indication for comparison of 2 numbers in magnitude.
         $ 9 and 3 quarters of dollars  = $ 9.75 = 975 C
          What is the sales  Tax paid on $ 50 purchase of the rate of nine and 3 quarter of a percent.
           $ 50 * 9 3/4 % =  50 * 9.75 % = 50 * 0. 0975 = $4.88    


In this case for percentage,find the ratio of the increase amount  to the stating value.  
Don't know the percentage value. But you know that percentage is a ratio, and could evaluate that .
Katie L. | Inspired Academic Help!Inspired Academic Help!
5.0 5.0 (233 lesson ratings) (233)
To find the percentage increase, first place the numbers given side by side 
For example:
Starting Value         Current Value
$400                       $470
Subtract the Starting value from the Current value
Divide the difference by the Starting value
Move the decimal two places to the right to form a percentage
I hope this helps!
Steve S. | Tutoring in Precalculus, Trig, and Differential CalculusTutoring in Precalculus, Trig, and Diffe...
5.0 5.0 (3 lesson ratings) (3)
Let's say you open a savings account and deposit $200.
One year later you find that your balance is $205.
The change in value is $205 - $200 = +$5.
The percent change in value is ($5/$200)(100) = 2.5% per year.