Beat The GMAT

taposh_dr · Sun Feb 07, 2010 5:49 am

Greetings all,

I got this compliation of furmulae from the web. Thought this might help.

Regards,

T

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papgust · Sun Feb 07, 2010 6:25 am

Wonderful! Thanks for sharing..!

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shashank.ism · Sun Feb 07, 2010 8:04 am

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jeffedwards · Mon Feb 08, 2010 7:19 pm

Thanks for the sheet that’s awesome. Just one word of caution, I quickly scanned this sheet and found one error. I haven’t noticed any others, but you may want to double check.

The sheet states that the area of an isosceles triangle is (1/2)(leg)^2. This can’t be. An isosceles triangle means that at least two sides are equal. So we could have sides of 8, 8, and 1. Or, we could have sides of 8, 8, 15. As you can see by plugging into the formula (area of a triangle is ((½)bh) just above, these triangles would have very different areas.

And no, that is not the formula for an equilateral triangle either.

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jeffedwards · Mon Feb 08, 2010 7:41 pm

Ok found another, the sheet says that in a square the diagonal is equal to the side squared (d=s^2). We know that’s not right. In a 45-45-90, the sides go as follows s-s-s√2. In other words d=s√2 NOT d=s^2.

I want you to know, I appreciate posts like this. Free study material is great!! Just don’t memorize formulas blindly.

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taposh_dr · Mon Feb 22, 2010 8:13 pm

Hey Jeff,

For the isosceles right triangle, the two equal sides are called as the legs i.e. 8 and 8 are your legs. I think the PDF needs to mention that its a right triangle and then the equation is valid.

Good catch though.

Regards,

T

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lunarpower · Tue Feb 23, 2010 5:01 am

a few random comments:

* the "intersecting chords" and "intersecting tangents/secants" formulas are outside the scope of the gmat.

* you also won't have to know how to calculate the lateral area of a cone.

* i'm not sure whether you have to know the sphere formulas, but i don't think you do (does anyone know about this for sure, either way?)

* some of these formulas are redundant enough to be a waste of your time and effort. for instance, if you know that the area of a circle is pi(r^2), then there is very little point in ALSO memorizing that it is pi(d^2/4), since it's so easy to calculate the radius if you have the diameter.

* on the other hand, some of the formulas are TREMENDOUS shortcuts, especially
- diagonal of a rectangular solid
- diagonal of a cube
- area of an equilateral triangle