Mathematics > Standard Multiple Choice
Read the following SAT test question and then click on a button to select your answer.
If x over 3 = x^2, the value of x can be which of the following?
roman numeral 1. negative 1 over 3
roman numeral 2. 0
roman numeral 3. 1 over 3
(A) roman numeral 1 only
(B) roman numeral 2 only
(C) roman numeral 3 only
(D) roman numeral 2 and roman numeral 3 only
(E) roman numeral 1, roman numeral 2, and roman numeral 3
The correct answer is D
Explanation
Roman Numeral Answer Format
Roman Numeral roman numeral 1: Can the value of x be negative 1 over 3?
You could test this answer by substituting negative 1 over 3 for x in the equation and seeing whether the result is true. But you can also reason this question out without substituting numbers:
If x = negative 1 over 3, then (negative (1 over 3))^2 is a positive number, because any nonzero number squared is positive.
If x = negative 1 over 3, then x over 3 is negative.
So x over 3 is negative and x^2 is positive.
Therefore, x cannot be negative 1 over 3.
Mark Roman numeral roman numeral 1 with an “F” for false.
Roman Numeral roman numeral 2: Can the value of x be 0?
This is a very easy substitution to make:
x over 3 = x^2
0 over 3 = 0^2 = 0
Roman numeral roman numeral 2 is true, so mark it with a “T” for true.
Roman Numeral roman numeral 3: Can the value of x be 1 over 3?
Substitute 1 over 3 for x:
If x = 1 over 3, then x over 3 = 1 over 9.
Also, x^2 = (1 over 3)^2 = 1 over 9.
Roman numeral roman numeral 3 is true, so mark it with a “T” for true.
Check the Answers:
You now know whether each of the Roman numeral statements is true or false:
roman numeral 1 is false.
roman numeral 2 is true.
roman numeral 3 is true.
Find the choice that says only roman numeral 2 and roman numeral 3 are true.