GRE Math Fact V.2
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What are the median and the mode of a set of data?
In a set of n numbers arranged in an increasing order, the median is the middle number (if n is odd), or the average of the two middle numbers (if n is even).
The mode is the number that appears most often.
What are the three most important binomial products?
- Memorize these three binomial products:
- (x+y)(x-y) = x2 -y2
- (x+y)2 = (x+y)(x+y) = x2 + 2xy + y2
- (x-y)2 = (x-y)(x-y) = x2 -2xy + y2
What is the measure of a straight angle?
The measure of a straight angle is 180o . If two or more angles form a straight angle, the sum of their measure is 180o .
What is the sum of the measures of all the angles around a point?
No matter how many angles there are, the sum of the measures of all the angles around a point is 360o .
What is true about the measures of the four angles formed by two intersecting lines?
When the two lines intersect, two pairs of opposite or vertical angles are formed. In each pair the two angles are equal.
What is true about the measures of the three angles in a triangle?
In any triangle, the sum of the measures of the three angles is 180o .
What is the relationship between the lengths of the sides of a triangle and the measures of the angles of the triangle?
- In any triangle:
- The longest side is opposite the largest angle.
- The shortest side is opposite the smallest angle.
- Sides with the same length are opposite angles with the same measure.
What is the Pythagoream theorem?
The Pythagorean theorm states that in a right triangle. the sum of the squares of the two legs is equal to the square of the length of the hypotenuse.
a2 + b2 = c2
What is the formula for the area of a triangle?
The formual for the area of a triangle is A = 1/2bh. Where b is the base and h is the height.
What is the ratio of similitude?
If two triangles are similar, the ratio of their corresponding sides is called the ratio of similitude. In those triangles, the ratio of all corresponding linear measurements are equal to the ratio of similitude.
What is true about the areas of simular triangles?
If two triangles are similar with a ratio of similitude of k, the ratio of their areas is k2 .
In a circle of radius r, what are the formulas for the diameter, the circumference , and the area of the circle?
- In a circle of radius r:
- The diameter is twice the radius: d = 2r
- The circumference is π times the diameter: C = πd.
- THe area of the circle is: A = π r2 .
What is the formula for the slope of a line on a graph?
slope = y2 - y1 / x2 - x1
How do you find the probability that an event will occur?
- If E represents any event, the probability that E will occur is:
- P(E) = number of favorable outcomes / total number of possible outcomes.
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