Percent Change = New Value − Old Value|Old Value| × 100%
Example: There were 200 customers yesterday, and 240 today:
240 − 200|200|× 100% = 40200 × 100% = 20%
A 20% increase.
Percent Error = |Approximate Value − Exact Value||Exact Value| × 100%
Example: I thought 70 people would turn up to the concert, but in fact 80 did!
|70 − 80||80| × 100% = 1080 × 100% = 12.5%
I was in error by 12.5%
(Without using the absolute value, the error is −12.5%, meaning I under-estimated the value)
The difference between the two is that one states factual calculations and the other is a theoretical guess
Answer: 
Step by step:
(Used a table of common angles)
Answer:
divide
Step-by-step explanation:
Answer:
the second graph (c)
Step-by-step explanation:
Answer:
20 green pencils
Step-by-step explanation:
The difference between black and green "ratio units" is 7 -5 = 2. The difference between red and blue ratio units is 3 -2 = 1. The sum of those differences is 2 +1 = 3 ratio units, which represent 12 pencils. Then each ratio unit represents 12/3 = 4 pencils.
The 5 ratio units of green pencils represent 5·4 pencils = 20 green pencils.
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If you need an equation, you can use k as the constant of proportionality. Then the sum of differences described is ...
(7k -5k) + (3k -2k) = 12
3k = 12 . . . . simplify
k = 4 . . . . . . divide by 3
5k = 5·4 = 20 . . . . . number of green pencils
