Percentage
Working with relative values.
Percentage can be calculated as
p = 100% P / W (1)
where
p = percentage (%)
P = part
W = whole
Example  Contractors Materials
A contractor spent an amount of 100000 for materials in a custom home project. The total cost of the project was 200000. The materials percentage cost can be calculated as
p = 100% (100000) / (200000)
= 50%
Example  Weight of Engine
Weight of an engine is 200 kg. The total weight of the car is 1500 kg. The percentage weight of the engine can be calculated as
p = 100% (200 kg) / (1500 kg)
= 13.3%
Example  Increasing Price
The cost of a contract increase from 100000 to 120000. The percentage increase of the contract price can be calculated as
p = 100% (120000  100000) / (100000)
= 20%
Example  Decreasing Price
The cost of a contract decrease from 100000 to 80000. The percentage decrease of the contract price can be calculated as
p = 100% (100000  80000) / (100000)
= 20%
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