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sheena87
Posts: **190**Registered User Junior Member

what r some formulas that r helpful for the sat other than the ones that are provided already in the math section ?

Post edited by sheena87 on

## Replies to: important math formulas

3,267Registered User Senior Member11Registered User New Memberits good to know calculator input functions - especially "solve"

saves a lot of time

11,791Registered User Senior Member161Registered User Junior MemberAnd another for distance/whatever - "dirt" (d=rt, distance=rate*time).

938Registered User Member1,414Registered User Senior MemberMost of the needed formulas are given, although there are some others, perhaps too "obvious" for many people here, such as: x^-n = 1/x^n ("^" means "to the power of"), average=sum/N, the difference of squares a^2-b^2=(a+b)(a-b), the distance formula (though this just comes from the pythagorean theorem), and so on.

By "facts" I mean things like: two lines intersecting make two angles that add to 180 degrees, an equilateral triangle has three angles of 60 degrees, the slope of a line is rise/run, etc. etc.

I've collected a pile of these facts along with the few formulas into short pdf files (free and non-commercial) on my web site; if people are interested, I'll post the link...

94Registered User Junior MemberOf course, these problems can also be solved using a bit of common sense, like any math problem on the SAT.....

3,267Registered User Senior MemberA car goes 25 miles per hour for 10 km, then goes 50 miles per hour for another 10 km (technically this is impossible, the car would have to accelerate from 25 to 50, but whatever). What's the average speed of the car? Now, by using the equation above, you get 33.3, while the answer is clearly 37.5 miles per hour.

I think a lot of people feel a sense of security when given an equation, because they think that that's all there is to it, when it requires thinking. Also a way lots of high school students approach math class--remember this formula, remember that equation, without any understanding of how basic equations arise and how they can be used.

3,447Registered User Senior Member89Registered User Junior Member94Registered User Junior MemberOP asked for "formulas that r helpful for the sat other than the ones that are provided already in the math section" - the formula for average rate happens to be one that I used on the March SAT.

Did it take "common sense" to know when/how to apply it? Yes.

Did it help to know the formula & its usage beforehand, given that the SAT is a timed test? Again, yes.

1,414Registered User Senior MemberMost of the remaining math you need to know is more factual (i.e., what an isosceles triangle is, slope-intercept line form, etc.) than formula-based.

I have to admit, I would never suggest that people memorize "2xy/(x+y)". This formula is very specific to one type of question that appears only occasionally. Even stronger students looking to save a little time would probably be better off knowing/learning the underlying concepts in that type of problem rather than that formula.

3,267Registered User Senior Member968Registered User Member58Registered User Junior Member