A percentage is really a division by a 100. Changing a percentage to a fraction means setting the denominator of the percentage to 100.
To turn a percentage into a fraction, create a fraction by setting the numerator to the percentage and the denominator to 100, then simplify that fraction.
Turn a fraction into a percentage by obtaining an equivalent fraction where the denominator is 100. The numerator represents the percentage.
Four-fifths of cars leaving a car park paid for parking for three hours or more. What is this as a percentage?
Make the denominator of the fraction a 100:
Multiply the numerator and denominator by 20 = `frac(80)(100)`.
The numerator is the answer as a percentage.
The pass mark on a test was 55%. Alex scored 31/60. Did he pass the test?
First change the denominator to be 100:
Multiply top and bottom by 10 = `frac(310)(600)`.
Then divide by 6 to set the denominator to 100: `frac(31)(100)`
His percentage score was 31%.
(You could also answer this question by changing the pass percentage into a fraction `frac(55)(100)` and setting the denominator to 60 = `frac(33)(60)`, and checking his score against the pass mark.)