Proportionality (mathematics) - Simple English Wikipedia, the free encyclopedia
There are 2 types of Proportionality: Direct and Inverse
With Direct Proportion, it's when 2 values are a multiple of another.
For example: 1cm= 10mm. To convert cm to mm, the multiplier always has to be 10.
Direct Proportion can be used to calculate the cost of petrol, or exchange rates of foreign money.
The symbol for Direct proportion is ∝.
The Statement ' t is directly proportional to r' can be written as t ∝ r.
With Inverse Proportion, one increases as the other decreases at the same rate. If one quantity doubles, the other one halves. For example, more workers on a job would reduce the time to complete the task. They are inversely proportional.