Percent Change vs. New Percent

[pscher31]

Can someone please clarify when to use the PC formula (PC=CV/OV) vs. the NP formula (NP=NV/OV). I'm having trouble identifying when to use each in PS questions. Some examples would be fantastic. Thanks in advance.

[Jim@StratusPrep]

By new percent, do you mean 'percent of'?

[pscher31]

Yes sorry, I meant percent of.

[Jim@StratusPrep]

Here is a start:

OG 13:

PS:

8
21
58
94
177
181

DS:
151

[ceilidh.erickson]

The best strategy is to stop thinking in terms of formulas, and think in terms of concepts instead!

Percent change - this will be asking you about the difference between an old situation and a new situation. Look for language of "percent increase," "percent decrease," or "percent change." This will indicate that you're comparing the change to the original:
percent change = (new - original)/original, or difference/original

#57. Company P had 15 percent more employees...
#71. ... the number of stocks... was 20 percent greater...
#94. ... what was the percent increase?
#114. ... what was the percent change?
#115. ... by approximately what percent did the ratio decrease?
#177. ... by what percent did the ratio of price per share increase?
#182. ... what was the approximate profit or loss...

Percent of - this will ask you to simply compare the new value to the original value, but not to calculate the difference. You basically just want to look for language of "percent of."
Percent of = new/original

#21. 150 is what percent of 30?
#58. ... what percent of the original...
# 123. ... what percent of Juan's income is Mary's?
#171. ... the remaining solution will be what percent sodium...