## Sunday, June 21, 2015

Do you know that you can make ‘magic’ with numbers on the MCAT?
First of all, know that your power comes from being efficient and by using pattern recognition.

1. For example, even with no context whatsoever, if you see 44.8 l or 11.2 l on the MCAT, your Pavlovian response should be: "I'm dealing with 2 moles (or 1/2 a mole) of a gas at STP."
Without reading the question, you recognize a multiple of 22.4 l (the molar volume, Avogadro's Law). Anything times 10 to the power of 23, instantly brings to mind Avogadro's number of particles (a multiple or fraction thereof).
It does not mean that 100% of the time the answer will depend on your Pavlovian response! We are looking at trends, likelihoods that occur rather often for those minority of questions that are number based.
Have you seen these numbers on some AAMC exams: 1.44, 1.69? Do they ring a bell? You should have memorized all squares between 1 and 15. You likely have 1 to 10 stone cold! 11 squared is 121, 12 -> 144, 13 -> 169, 14 -> 196, 15 -> 225. They choose their numbers carefully. The moment you see 1.44 on the MCAT, there is a high likelihood that you would be required to take the square root which gives 1.2. Pattern recognition.

2.  A little blast from the past: pi is 3.14, root 2 is 1.4, root 3 is 1.7. Do not be surprised if you need to calculate the perimeter (2 pi r) or area (pi r squared) of a circle. Be comfortable estimating the root of anything! Root 17? Well, the answer must be between 4 and 5 but closer to 4. Check the answers and do not calculate anything if there is only one answer that is between 4 and 4.5.

3. Avoid decimals until you have no choice. Fractions will usually permit you to be more efficient. For huge and tiny numbers, you need to be comfortable with scientific notation. If you can hang on to variables for as long as possible, that's even better. You may be surprised how many times mass m ends up being irrelevant as it happily cancels out!
Feel free to share the above information to other students.