Sales fall from 300 per week to 270 per week what’s the percentage change

Hi there! 

Your question: 

Sales fall from 300 per week to 270 per week what's the percentage change?

My

The formula for calculating percent change is as follows: 

[(y2 - y1)/y1]*100=your percent change 

y2= first value 
y1=second value 

Plug the numbers in: 

[(300-270)/300]*100

[30/300]*100

0.1*100

10 

Therefore, the percent change is 10%

Hope this helps! Let me know if it's incorrect so I can fix it:)