Clarification on the meaning of "number of decimal places" I've learned in school that the "number of decimal places" in a number refers to how many digits are after the decimal point.
For example, 2.5 and 100.2 have 1 decimal place, and 0.234 has 3.
But what about numbers like 56. and 45.0? Do numbers like that have 0 or 1 decimal places?
(Also, please correct me if I'm misunderstanding decimal places in my question)

The "number of decimal places" is not a property of the number itself, but about how it is written. So $1.$ has zero d.p. and $1.0$ has one, though they are numerically equivalent.
