SAT Math Question of the Day

Math Category: Exponents:

Q: 2n + 2n = ?

  1. 2(n + 1)
  2. 2(n2)
  3. 2(2n)
  4. 4(2n)
  5. 4(n n)

UNANSWERED.

The correct answer is A.

A: 2(n + 1)

Remember these rules:

  1. If the base (x) is the same and you're multiplying, you add the exponents.
  2. If the base (x) is the same and you're dividing, you minus the exponents.
2n + 2n = 2 * (2n) = 21 * 2n = 2(n+1) In this case, the base is 2, and we're multiplying 21 * 2n, so we add the exponents.

If you don't remember the exponent rules, then Choose Any Number. So say you choose n = 2. Remember, any number will do, but try to pick a convenient number, one that's small, but not 0 or 1.
Plug in n = 2 into 2n + 2n = 22 + 22 = 8
Plug in n = 2 into the possible answers:

  1. 2(n + 1) = 2(2 + 1) = 23 = 8. It matches. But let's hold on and see whether there is another possible answer.
  2. 2(n2) = 2(22) = 24 = 16. Nope.
  3. 2(2n) = 2(2*2) = 24 = 16. No again.
  4. 4(2n) = 4(2*2) = 44. Too high.
  5. 4(n n) = 4(2*2) = 44. Too high.

A) is the only possible answer.