# Practice Math Questions for Praxis: Identifying Functions

Can you identify a function? If yes, then you’ll have no problem with function-related questions on the Praxis Core exam. If no, then you may want to brush up on your function-spotting skills, starting with the following practice questions.

## Practice questions

- Is the relation {(2, 5), (3, 7), (4, 1), (8, 1)} a function?
**A.**The relation is a function because no element of the range is paired with more than one element of the domain.

**B.**The relation is a function because no element of the domain is paired with more than one element of the range.

**C.**The relation is NOT a function because 1 is paired with both 4 and 8.

**D.**The relation is NOT a function because no element of the domain is paired with more than one element of the range.

**E.**The relation is NOT a function because 2 is paired only with 5. - Does the following mapping represent a function?

**A.**It does represent a function because each number in the domain is paired with at least one number in the range.

**B.**It does represent a function because each number in the range is paired with at least one number in the domain.

**C.**It does NOT represent a function because 2 is paired with both 1 and 12.

**D.**It does NOT represent a function because 5 is paired with both 7 and 10.

**E.**It does represent a function because no number is listed more than once in the left column.

## Answers and explanations

- The correct answer is Choice
**(B).**

None of the domain numbers (first numbers in the ordered pairs) are paired with more than one range element. In other words, no first number is repeated with a different second number, so the relation is a function. - The correct answer is Choice
**(D).**

The domain element 5 is paired with 7 and 10. It’s therefore paired with more than one range element, so it isn’t a function. Choices (A), (B), and (E) are incorrect because they have the wrong conclusion and false definitions of*function.*Choice (C) has the right conclusion but a false definition.