SAT Math Question of the Day

Q: n is an integer. Which is always odd?

1. n
2. n + 1
3. 2n
4. 2n + 1
5. n²

UNANSWERED.

The correct answer is D.

A: The answer is 2n + 1.

Not A) Since n is an integer it can be even or odd.

Not B) Correspondingly, adding 1 to n flips whether it's odd or even.

Not C) If you double any number it becomes even. Try it:
2 × 1 = 2,
2 × 2 = 4,
2 × 3 = 6.
It also works with a negative n:
2 × -1 = -2,
2 × -2 = -4.

D) If 2n is always even, then adding 1 to it, makes it always odd.

E) If n is even, n² is even. However, if n is odd, n² is odd. Let's see: