- 50⁄100 = 1⁄2
- 75⁄100 = 3⁄4
- = x⁄1003⁄4, where x = 75.
In algebra, proportions can be used to solve many common problems about changing numbers. As an example, for the increase in a $40 purchase of gasoline (petrol), if the price rose 35 cents, from $3.50 to $3.85, the proportion would be:
- = x⁄3.85$40⁄3.50
The solution is simply:
- x = $40/3.50 x 3.85 = $44.00, or $4 more when $0.35 higher.
Many other common calculations can be solved by using proportions to show the relationships between the numbers.