You can solve this type of calculation with your own values by entering them into the calculator's fields, clicking 'calculate' and getting your answer!
Percentages are similar to fractions with an important difference. In fractions the whole is represented by the denominator (e.g. the number 5 in the fraction of 1/5) In percentages, the whole is represented by the number 100. In fact, "per cent" means "per 100" or "for each 100."
To solve the problem above, let’s convert it into equation form: __ = 20% x 90
In this example, the number 90 represents the whole and so, as a percentage, it would be equal to 100%. Written as a ratio, we would get: 100% : 90
If a student took a 90 question test and they got every answer correct, as a percentage they would get a 100% score on the test.
In our problem we have to evaluate the 20 percent of 90. For now, let’s call this unknown value "Y". Written as a ratio, we would get: 20% : Y
To see a relationship between these two ratios, let’s combine them into an equation: 100% : 90 = 20% : Y
It is critical that both of the % values should be on the same side of a ratio. For instance, if you decide to put the % value on the right side of a ratio, then the other % value should also be on the right side of its ratio.
"90 : 100% and Y : 20%" is correct.
"90 : 100% and 20% : Y" is wrong.
Let’s solve the equation for Y by first rewriting it as: 100% / 90 = 20% / Y
Drop the percentage marks to simplify your calculations: 100 / 90 = 20 / Y
Multiply both sides by Y to transfer it on the left side of the equation: Y ( 100 / 90 ) = 20
To isolate Y, multiply both sides by 90 / 100, we will have: Y = 20 ( 90 / 100 )
Computing the right side, we get: Y = 18
This leaves us with our final answer: 20% of 90 is 18