If you are reading this in an email you received from me, do not click the link to sat.collegeboard.org below. Use the link to my website that is farther down on the email.
http://sat.collegeboard.org/practice/sat-question-of-the-day?questionId=20140317&oq=1 (This link takes you to today’s question. If you use my archive, you will see the question related to my SAT explanation for that date.)
One thing this question tells us about the test writers is that if there is a way to do the question that takes a lot of time, they’ll show it to you!
The answer is E. Yes, you can do it their way but why waste the time and run the risk of making a silly math mistake? There are at least three quicker ways to do the problem. First, whenever a question asks, “What is the value of…,” try the answers and start with C because it is in the middle. 5-2 is 3 and its square root is going to be less than 2; so, when you add 5, you know right away it is much smaller than 9. Try a larger answer, D (16). 16-3 is going to be 13 and its square root is less than 4 which means it is still too small when we add 5. This is cool! We’ve only tried two answers and we know the answer has to be E, 19, without even trying it because we’ve already eliminated 4 answers. However, let’s check to make sure we are right. 19 – 3 is 16 and its square root is 4. 4 + 5 is 9. Yep, we were right. E, 19, is the right answer.
Second, my wife, Dr. Alexander, (the college admissions coach for our charity) did it by working backwards from 9. Subtract 5 and you have 4. Square 4 and you have 16. Add 3 to 16 and you get 19, Answer E. That was sure a lot faster than the test writer’s way to do the question.
Third, there’s an even faster way to do this question. All the numbers are integers. That means when you subtract 3 from x, you have to end up with a perfect square! That leaves you with x=19 because none of the other answers meet this requirement. (Answer A, 3, kind of works but 3 – 3 = 0 and you can quickly see 0 + 5 is not equal to 9. However, 0 isn’t a perfect square because the strict definition of a perfect square is that it is a number with a positive integer for a square root and 0 isn’t positive — or negative.) That leaves us with 19 – 3 = 16, a perfect square with a root of 4 and 4 + 5 = 9. All done.
It took less than 5 seconds to get this answer after reading the question. Why would you bother to do it the test writer’s way? (It is a little faster than Dr. Alexander’s way because she had to go back to read and work through the question very carefully. However, I sure like what she did!) The SAT and ACT are both full of these kinds questions that can be done very quickly with a little reasoning rather than a lot of calculations. These strategies will save you a lot of time. Practice is going to help you learn to recognize them. Get to work.
I wonder if the ACT folks have something new for us this morning.
ACT Question of the Day: Use your “back” button to return to my website after reading the ACT Question of the Day.
No, they don’t. That wasn’t any fun. I remembered the answer is C because I’ve seen this question way too many times. Let’s pretend I haven’t seen it before.
The answer is C. At 100 years, pine trees have decreased, leaving us with answers C and D. “Oak-hickory trees” have increased leaving us with answer C. (By the way, what in the world is an “oak-hickory” tree, some kind of hybrid? The answer should be about an “oak-hickory forest” or “oak and hickory trees,” but I guess the ACT test writers, who are in Iowa, are too used to counting corn. Don’t they even know that oak trees and hickory trees can’t breed? Maybe they don’t know the difference been “trees” and “forest!” Maybe they “can’t see the forest for the trees.”)
What can we learn from this question about the test? First, don’t bother to review science concepts. Second, the questions on the test are answered by the information you are given in the science passages. Third, practice reading charts and graphs. The test writers use lots of ways to depict data and you need to practice their released tests in order to see the numerous ways they do that. Again, “practice rules.”
I hope you have a spectacular week.
Bob Alexander, the “SAT and ACT Wizard”