9/90 = 10%
A value like 9/90, or 10%, can show up in everyday life as a discount, test score, tip, or chance of an event happening. For example, a store might take 10% off a $90 purchase, or a weather report might say there is a 10% chance of rain.
You can picture 10% as one part out of ten equal parts. It is also easy to estimate as a small slice of the whole—about the amount you would get by dividing something into ten groups and choosing one group.
A common mistake is thinking 9/90 is close to 9% because of the 9 in the numerator. The denominator matters too, since it represents the total number of equal parts, and 9 out of 90 is the same share as 1 out of 10.
