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GRE Math Rules

Subjects : gre, math

Instructions:

Answer 50 questions in 15 minutes.
If you are not ready to take this test, you can study here.
Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. vertical angles
Last three digits (taken together) are divisible by 8
x^(a-b) or a/x^(b-a)
1 - 1 - root(2)
Opposite angles formed by two intersecting lines; always congruent

2. permutations of n different objects
2(pir^2) + 2pirh; the two bases and the side
N(n-1)(n-2)...(2)(1) = n!
N!/(n-k)!
Opposite angles formed by two intersecting lines; always congruent

3. (x^a)(y^a)
Any line connecting two points on a circle. The diameter is a chord
2(pir^2) + 2pirh; the two bases and the side
(xy)^a
1098 etc

4. standardization/normalization
Always equal - i.e. 9 choose 3 = 9 choose 6
A list is ordered and can have duplicates
Subtract the mean from each value and divide by the standard deviation
(n-2)(180 degrees)

5. isosceles triangle
Area of sector has the same proportion to the total area that the arc measure (angle) has to 360 degrees.
At least two congruent sides; the angles opposite these sides are also congruent
2(pir^2) + 2pirh; the two bases and the side
The sum of the areas of the six faces: 2(lw + lh + wh)

6. probability of an event E
1
(x^a)/(y^a)
(xy)^a
Number of outcomes yielding E / number of total outcomes

7. area of circle
Congruent angles (check this to be sure) but possibly different size. Can use proportions to get other values by cross-multiplication
The sum of the areas of the six faces: 2(lw + lh + wh)
Pi * r^2
At least two congruent sides; the angles opposite these sides are also congruent

8. circumference of circle
Area of sector has the same proportion to the total area that the arc measure (angle) has to 360 degrees.
2pi*r
Side opposite the right angle
Pi*r^2h

9. advantage of median
x^(a-b) or a/x^(b-a)
Less affected by outliers than the mean
2(pir^2) + 2pirh; the two bases and the side
A + B - their intersection

10. possible combinations of three digits without allowing repeats
Still bh/2 - but you can draw h as a line perpendicular to an extension of any side you take as the base.
1098 etc
Base * height
Three sides congruent - two sides and included angle - two angles and included side

11. divisible by 9
(n-2)(180 degrees)
Last three digits (taken together) are divisible by 8
Sum of its digits is divisible by 9
Invert the second fraction and multiply them

12. area of cylinder
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.
At least two congruent sides; the angles opposite these sides are also congruent
x^(a-b) or a/x^(b-a)
2(pir^2) + 2pirh; the two bases and the side

13. chord
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.
P(E and F) = P(E)P(F)
Sum of its digits is divisible by 3
Any line connecting two points on a circle. The diameter is a chord

14. regular polygon
All its interior angles are congruent
Subtract the mean from each value and divide by the standard deviation
P(E and F) = P(E)P(F)
1/2(b1 + b2)h - where b1 and b2 are the two parallel sides

15. combinations of n objects taken k at a time (order doesn'T count)
N(n-1)(n-2)...(2)(1) = n!
N!/(n-k)!
Lwh
N!/k!(n-k)! which is also denotes as n choose k

16. what'S the median if there are an even number of data points?
Base * height
Mean of the two middle ones
1/2 base * height
Subtract the mean from each value and divide by the standard deviation

17. area of trapezoid
1/2 base * height
1/2(b1 + b2)h - where b1 and b2 are the two parallel sides
Subtract the mean from each value and divide by the standard deviation
N(n-1)(n-2)...(2)(1) = n!

18. mutually exclusive
|S|
A + B - their intersection
P(E or F) = P(E) + P(F)
Base * height

19. divisible by 6
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.
Rules for 2 and three: even and the sum of its digits is divisible by three
A + B - their intersection
P(E) + P(F) - P(E and F)

20. divisible by 4
Last three digits (taken together) are divisible by 8
Last two digits (taken together) are divisible by 4
1098 etc
Pi * r^2

21. relationship between n choose k and n choose n-k
Always equal - i.e. 9 choose 3 = 9 choose 6
At least two congruent sides; the angles opposite these sides are also congruent
Any line connecting two points on a circle. The diameter is a chord
Pi*r^2h

22. differences between a set and a list
1/2 base * height
Sum of its digits is divisible by 3
1 - 2 - root(3); note that this is half of an equilateral triangle
A list is ordered and can have duplicates

23. congruency of triangles
P(E) + P(F) - P(E and F)
2(pir^2) + 2pirh; the two bases and the side
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.
Three sides congruent - two sides and included angle - two angles and included side

24. (x^a)^b
x^ab
Sum of its digits is divisible by 3
Always equal - i.e. 9 choose 3 = 9 choose 6
Opposite angles formed by two intersecting lines; always congruent

25. area of parallelogram
Base * height
P(E and F) = P(E)P(F)
Rules for 2 and three: even and the sum of its digits is divisible by three
1 - 1 - root(2)

26. sum of relative frequencies in a frequency distribution
P(E or F) = P(E) + P(F)
1 if decimals - 100 if percents
Area of sector has the same proportion to the total area that the arc measure (angle) has to 360 degrees.
x^ab

27. dividing fractions
(x^a)/(y^a)
x^ab
x^(a-b) or a/x^(b-a)
Invert the second fraction and multiply them

28. (x^a)(x^b)
Invert the second fraction and multiply them
A list is ordered and can have duplicates
x^(a+b)
1/2 base * height

29. area of rectangle
Length of arc has the same proportion to the circumference that the arc measure (angle) has to 360 degrees.
The sum of the areas of the six faces: 2(lw + lh + wh)
Subtract the mean from each value and divide by the standard deviation
Divide it by the prime numbers from 2 to the closest to the square root of the number (round down).

30. sides of 30/60/90 triangle
Pi * r^2
1 - 1 - root(2)
Sum of its digits is divisible by 3
1 - 2 - root(3); note that this is half of an equilateral triangle

31. possible combinations of three digits allowing repeats
1 if decimals - 100 if percents
At least two congruent sides; the angles opposite these sides are also congruent
101010
Rules for 2 and three: even and the sum of its digits is divisible by three

32. volume of rectangle
(x^a)/(y^a)
P(E or F) = P(E) + P(F)
Lwh
1/2(b1 + b2)h - where b1 and b2 are the two parallel sides

33. how to tell if something is prime
1098 etc
Divide it by the prime numbers from 2 to the closest to the square root of the number (round down).
101010
(xy)^a

34. x^-a
Always equal - i.e. 9 choose 3 = 9 choose 6
1
1/x^a
1/2 base * height

35. union of sets A and B
x^ab
Still bh/2 - but you can draw h as a line perpendicular to an extension of any side you take as the base.
A + B - their intersection
P(E) + P(F) - P(E and F)

36. area of sector of circle
Side opposite the right angle
N-2
(x^a)/(y^a)
Area of sector has the same proportion to the total area that the arc measure (angle) has to 360 degrees.

37. hypotenuse
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.
Side opposite the right angle
A + B - their intersection
Sum of its digits is divisible by 9

38. divisible by 8
All its interior angles are congruent
Last three digits (taken together) are divisible by 8
Divide it by the prime numbers from 2 to the closest to the square root of the number (round down).
1

39. (x^a)/(x^b)
Subtract the mean from each value and divide by the standard deviation
x^(a-b) or a/x^(b-a)
Side opposite the right angle
The sum of the areas of the six faces: 2(lw + lh + wh)

40. permutations of n objects taken k at a time (order counts)
N!/(n-k)!
|S|
N!/k!(n-k)! which is also denotes as n choose k
Sum of its digits is divisible by 9

41. (x/y)^a
Invert the second fraction and multiply them
Sum of its digits is divisible by 3
At least two congruent sides; the angles opposite these sides are also congruent
(x^a)/(y^a)

42. difference between normal or population standard deviation and the sample standard deviation
Sum of its digits is divisible by 3
Invert the second fraction and multiply them
P(E) + P(F) - P(E and F)
In computing the average squared difference from the mean (taking the root of this is the standard deviation) - divide by n-1 instead of n

43. divisible by 3
Pi*r^2h
Sum of its digits is divisible by 3
Invert the second fraction and multiply them
1098 etc

44. x^0
P(E or F) = P(E) + P(F)
1
P(E) + P(F) - P(E and F)
N!/(n-k)!

45. divisible by 11
1/x^a
Congruent angles (check this to be sure) but possibly different size. Can use proportions to get other values by cross-multiplication
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.
1/2 base * height

46. independence of two events E and F
P(E and F) = P(E)P(F)
(x^a)/(y^a)
Length of arc has the same proportion to the circumference that the arc measure (angle) has to 360 degrees.
Still bh/2 - but you can draw h as a line perpendicular to an extension of any side you take as the base.

47. number of elements in set S
(x^a)/(y^a)
101010
|S|
Pi * r^2

48. volume of cylinder
Length of arc has the same proportion to the circumference that the arc measure (angle) has to 360 degrees.
Base * height
Pi*r^2h
Lwh

49. sides of isoceles right triangle
x^ab
1 - 1 - root(2)
Lwh
x^(a-b) or a/x^(b-a)

50. how many triangles can a polygon of n sides be divided into?
(x^a)/(y^a)
Pi * r^2
1 - 2 - root(3); note that this is half of an equilateral triangle
N-2