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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. independence of two events E and F
P(E and F) = P(E)P(F)
2(pir^2) + 2pirh; the two bases and the side
Still bh/2 - but you can draw h as a line perpendicular to an extension of any side you take as the base.
P(E) + P(F) - P(E and F)

2. sum of relative frequencies in a frequency distribution
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
P(E and F) = P(E)P(F)
At least two congruent sides; the angles opposite these sides are also congruent
1 if decimals - 100 if percents

3. congruency of triangles
2pi*r
Sum of its digits is divisible by 9
Last three digits (taken together) are divisible by 8
Three sides congruent - two sides and included angle - two angles and included side

4. x^0
|S|
1098 etc
101010
1

5. area of cylinder
2(pir^2) + 2pirh; the two bases and the side
x^ab
Invert the second fraction and multiply them
Any line connecting two points on a circle. The diameter is a chord

6. sides of 30/60/90 triangle
1 - 2 - root(3); note that this is half of an equilateral triangle
Opposite angles formed by two intersecting lines; always congruent
A list is ordered and can have duplicates
Three sides congruent - two sides and included angle - two angles and included side

7. how to tell if something is prime
A list is ordered and can have duplicates
Divide it by the prime numbers from 2 to the closest to the square root of the number (round down).
Subtract the mean from each value and divide by the standard deviation
P(E and F) = P(E)P(F)

8. isosceles triangle
At least two congruent sides; the angles opposite these sides are also congruent
1098 etc
x^(a+b)
Pi*r^2h

9. divisible by 8
Mean of the two middle ones
Last three digits (taken together) are divisible by 8
Sum of its digits is divisible by 9
1 - 1 - root(2)

10. advantage of median
Always equal - i.e. 9 choose 3 = 9 choose 6
Any line connecting two points on a circle. The diameter is a chord
Invert the second fraction and multiply them
Less affected by outliers than the mean

11. similar triangles
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.
Subtract the mean from each value and divide by the standard deviation
Length of arc has the same proportion to the circumference that the arc measure (angle) has to 360 degrees.

12. divisible by 3
Last three digits (taken together) are divisible by 8
Sum of its digits is divisible by 3
x^ab
A list is ordered and can have duplicates

13. relationship between n choose k and n choose n-k
Sum of its digits is divisible by 3
Sum of its digits is divisible by 9
x^(a-b) or a/x^(b-a)
Always equal - i.e. 9 choose 3 = 9 choose 6

14. (x^a)(x^b)
1 if decimals - 100 if percents
A list is ordered and can have duplicates
Side opposite the right angle
x^(a+b)

15. differences between a set and a list
A list is ordered and can have duplicates
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.
Pi * r^2
Always equal - i.e. 9 choose 3 = 9 choose 6

16. union of sets A and B
N!/(n-k)!
x^(a-b) or a/x^(b-a)
N!/k!(n-k)! which is also denotes as n choose k
A + B - their intersection

17. vertical angles
Less affected by outliers than the mean
Opposite angles formed by two intersecting lines; always congruent
1 - 1 - root(2)
Three sides congruent - two sides and included angle - two angles and included side

18. area of rectangle
The sum of the areas of the six faces: 2(lw + lh + wh)
Divide it by the prime numbers from 2 to the closest to the square root of the number (round down).
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.
Mean of the two middle ones

19. circumference of circle
Sum of its digits is divisible by 3
1/x^a
101010
2pi*r

20. possible combinations of three digits without allowing repeats
1098 etc
(n-2)(180 degrees)
Last three digits (taken together) are divisible by 8
The sum of the areas of the six faces: 2(lw + lh + wh)

21. standardization/normalization
Lwh
Subtract the mean from each value and divide by the standard deviation
(n-2)(180 degrees)
P(E) + P(F) - P(E and F)

22. mutually exclusive
Rules for 2 and three: even and the sum of its digits is divisible by three
P(E or F) = P(E) + P(F)
All its interior angles are congruent
2(pir^2) + 2pirh; the two bases and the side

23. combinations of n objects taken k at a time (order doesn'T count)
N!/k!(n-k)! which is also denotes as n choose k
Mean of the two middle ones
Sum of its digits is divisible by 3
Length of arc has the same proportion to the circumference that the arc measure (angle) has to 360 degrees.

24. length of arc of circle
x^(a+b)
Three sides congruent - two sides and included angle - two angles and included side
Invert the second fraction and multiply them
Length of arc has the same proportion to the circumference that the arc measure (angle) has to 360 degrees.

25. sum of measures of interior angles of a polygon with n sides
P(E or F) = P(E) + P(F)
1/2 base * height
Length of arc has the same proportion to the circumference that the arc measure (angle) has to 360 degrees.
(n-2)(180 degrees)

26. probability that either E or F occur
P(E) + P(F) - P(E and F)
2(pir^2) + 2pirh; the two bases and the side
Less affected by outliers than the mean
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.

27. volume of rectangle
Sum of its digits is divisible by 3
Last three digits (taken together) are divisible by 8
1098 etc
Lwh

28. dividing fractions
Sum of its digits is divisible by 3
Invert the second fraction and multiply them
Base * height
Pi * r^2

29. divisible by 9
At least two congruent sides; the angles opposite these sides are also congruent
Sum of its digits is divisible by 9
P(E or F) = P(E) + P(F)
1/2 base * height

30. regular polygon
Last three digits (taken together) are divisible by 8
All its interior angles are congruent
N(n-1)(n-2)...(2)(1) = n!
Divide it by the prime numbers from 2 to the closest to the square root of the number (round down).

31. area of trapezoid
N!/k!(n-k)! which is also denotes as n choose k
1/2(b1 + b2)h - where b1 and b2 are the two parallel sides
x^ab
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.

32. divisible by 4
Last two digits (taken together) are divisible by 4
Opposite angles formed by two intersecting lines; always congruent
P(E or F) = P(E) + P(F)
Invert the second fraction and multiply them

33. how many triangles can a polygon of n sides be divided into?
N-2
x^ab
x^(a-b) or a/x^(b-a)
x^(a+b)

34. divisible by 11
Lwh
|S|
(xy)^a
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.

35. x^-a
2(pir^2) + 2pirh; the two bases and the side
N(n-1)(n-2)...(2)(1) = n!
1/x^a
N!/k!(n-k)! which is also denotes as n choose k

36. probability of an event E
Lwh
All its interior angles are congruent
(n-2)(180 degrees)
Number of outcomes yielding E / number of total outcomes

37. divisible by 6
Rules for 2 and three: even and the sum of its digits is divisible by three
Last three digits (taken together) are divisible by 8
Always equal - i.e. 9 choose 3 = 9 choose 6
Congruent angles (check this to be sure) but possibly different size. Can use proportions to get other values by cross-multiplication

38. area of circle
Three sides congruent - two sides and included angle - two angles and included side
|S|
1
Pi * r^2

39. difference between normal or population standard deviation and the sample standard deviation
At least two congruent sides; the angles opposite these sides are also congruent
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
P(E) + P(F) - P(E and F)
1/x^a

40. (x^a)/(x^b)
Sum of its digits is divisible by 9
N-2
x^(a-b) or a/x^(b-a)
Still bh/2 - but you can draw h as a line perpendicular to an extension of any side you take as the base.

41. permutations of n different objects
|S|
Always equal - i.e. 9 choose 3 = 9 choose 6
2(pir^2) + 2pirh; the two bases and the side
N(n-1)(n-2)...(2)(1) = n!

42. number of elements in set S
Subtract the mean from each value and divide by the standard deviation
Pi * r^2
1/2 base * height
|S|

43. sides of isoceles right triangle
Pi * r^2
1/2(b1 + b2)h - where b1 and b2 are the two parallel sides
Still bh/2 - but you can draw h as a line perpendicular to an extension of any side you take as the base.
1 - 1 - root(2)

44. hypotenuse
Side opposite the right angle
Any line connecting two points on a circle. The diameter is a chord
Subtract the mean from each value and divide by the standard deviation
Pi*r^2h

45. (x^a)(y^a)
x^(a-b) or a/x^(b-a)
(xy)^a
Number of outcomes yielding E / number of total outcomes
(x^a)/(y^a)

46. chord
Mean of the two middle ones
Always equal - i.e. 9 choose 3 = 9 choose 6
Any line connecting two points on a circle. The diameter is a chord
Base * height

47. area of triangle
Base * height
x^(a+b)
Divide it by the prime numbers from 2 to the closest to the square root of the number (round down).
1/2 base * height

48. area of sector of circle
Area of sector has the same proportion to the total area that the arc measure (angle) has to 360 degrees.
x^ab
1 - 1 - root(2)
Always equal - i.e. 9 choose 3 = 9 choose 6

49. what'S the median if there are an even number of data points?
N(n-1)(n-2)...(2)(1) = n!
Last two digits (taken together) are divisible by 4
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.
Mean of the two middle ones

50. area of parallelogram
Base * height
(1st digit + 3rd + 5th...) - (2nd + 4th + 6th...) is divisible by 11.
P(E) + P(F) - P(E and F)
101010