

September 1, 2016 at 1:48 pm #2652Mike KimKeymaster
Hey everyone —
I got an email from a student who is having trouble with the math inferences drill on page 165 — I get asked about that a lot, and I figured some of you might find it helpful if I posted my answer publicly —
The drill has to do with making numerical inferences — figuring out how many people from each group get selected based on the clues given.
This is a type of math that is really based on being able to visualize the situation (as opposed to, say, math that requires us to utilize a bunch of written formulas) —
And if you trouble visualizing, it can help to feed your brain actual visuals that it can use (and reference in future situations) —
So, with all that said —
One thing I would suggest is to try solving the drills by actually creating physical pieces that get placed — you can use notecards, or cut up pieces of paper, or whatever —
So, for the first exercise, you can put A on a few cards, B on a few cards, and C on a few cards.
Then, knowing that the total number of cards selected for any one problem must equal 5, use the cards you made to figure out the answer —
So, for example, for the first problem, we are told that we have 1 A and 1 or 2 C.
Using our cards, if we put in 1 A card and 1 C card, in order to get to 5, we need to put in 3 B cards. If we put in 1 A and 2 C, we need to put in 2 B.
So, when we know that there is 1 A and 1 or 2 C’s, we know we can either have 3 or 2 B’s.
For the second problem, we know we have 0 A’s and either 0, 1, or 2 B’s. Again, we can use the cards to figure out how many C’s we need.
With 0 A’s and 0 B’s, we need 5 C’s.
With 0 A’s and 1 B, we need 4 C’s.
With 0 A’s and 2 B’s, we need 3 C’s.So those are our answers — we can have 3, 4, or 5 C’s.
If you do this for a bit with the cards, you’ll start to develop a much better sense of how the math works, and you’ll be better able to just mentally visualize the situation — and soon enough you will feel comfortable doing the same work without the cards in front of you.
I know the above may seem a bit silly, especially if you are old like me and haven’t done stuff like this in a long time, but again, keep in mind that the math on the LSAT is much more about logic and visualization than it is about actual computation, and I think the above exercise can really help with that —
If you agree, then I also suggest something similar for game types that cause you trouble — try actually creating pieces (cards with letters on them), move them around to think about where they can go, and so on — you don’t have to do it a ton, but if you do it a few times, I think you may find yourself much more comfortable visualizing and playing around with that type of game in general —
Hope that helps and if anyone has any followup q’s just let me know —
Mike

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