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GRE Math: Common Errors

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. What is the formula for compounded interest?
A= I (1 + (r/c))^tC - where I is the investment - C is the number of times compounded annually - and t is the number of years.
1 & 37/132
The set of output values for a function.
10

2. What is the side length of an equilateral triangle with altitude 6?
2 & 3/7
5 OR -5
4sqrt3. The triangle can be divided into two equal 30-60-90 triangles with side 6 as the side in which 6 = xsqrt3. So x =2sqrt3...
1.0843 X 10^11

3. 40 < all primes<50
41 - 43 - 47
The union of A and B.
180 degrees
The shortest arc between points A and B on a circle'S diameter.

4. 1/6 in percent?
3
(a - b)(a + b)
16.6666%
1.7

5. What are congruent triangles?
x^(6-3) = x^3
(a + b)^2
C = (pi)d
Triangles with same measure and same side lengths.

6. How to find the diagonal of a rectangular solid?
4sqrt3. The triangle can be divided into two equal 30-60-90 triangles with side 6 as the side in which 6 = xsqrt3. So x =2sqrt3...
Expressing a number as the product of a decimal between 1 and 10 - and a power of 10.
(a + b)^2
Use Pythagorean theorem twice. (Once across the surface and then a is the diagonal of surface and b is an edge).

7. What is a major arc?

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8. How many multiples does a given number have?
The greatest value minus the smallest.
An infinite set.
When we need to avoid having a zero in the denominator or avoid taking the square root of a number.
Infinite.

9. What is the slope of a vertical line?

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10. a^2 - b^2 =
(a - b)(a + b)
Sqrt 12
3
PEMDAS (Parentheses Exponents Multiplication/Division Addition/Subtraction)

11. If Madagascar'S exports totaled 1.3 billion in 2009 - and 4% came from China - what was the value in millions of the country'S exports to China?
III
An algebraic expression is a combination of one of more terms. Terms in an expression are separated by either addition or subtraction signs. (3xy - 4ab - -5cd - x^2 + x - 1)
52
12sqrt2

12. What is a tangent?
A tangent is a line that only touches one point on the circumference of a circle.
The sum of digits is divisible by 9.
(a + b)^2
6 : 1 : 2

13. Formula for the area of a circle?
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
2^9 / 2 = 256
A = pi(r^2)
(a - b)(a + b)

14. Circumference of a circle?
Its last two digits are divisible by 4.
Diameter(Pi)
71 - 73 - 79
A = pi(r^2)

15. Legs 6 - 8. Hypotenuse?
10
Sqrt 12
The set of input values for a function.
130pi

16. Ratio of ages of Anna and Emma is 3:5 and of Emma and Nicolas is 3:5. What is the ratio of Anna to Nicholas' ages?
12sqrt2
(a - b)(a + b)
10! / (10-3)! = 720
9 : 25

17. 20<all primes<30
9 & 6/7
F(x) - c
23 - 29
1/2 times 7/3

18. What is the set of elements found in both A and B?
Ax^2 + bx + c where a -b and c are constants and a /=0
The interesection of A and B.
A circle centered at -2 - -2 with radius 3.
87.5%

19. In a triangle inscribed inside a circle - where the diameter is one side of the triangle - which angle is largest?
71 - 73 - 79
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
(a - b)(a + b)
A central angle is an angle formed by 2 radii.

20. What are the integers?
All numbers multiples of 1.
When we need to avoid having a zero in the denominator or avoid taking the square root of a number.
180
The set of elements which can be found in either A or B.

21. What are the members or elements of a set?
Angle/360 x (pi)r^2
Factors are few - multiples are many.
The objects within a set.
C = (pi)d

22. How many digits are there between the decimal point and the first even digit in the decimal equivalent of 1/[(2^8)(5^3)]
52
0
An arc is a portion of a circumference of a circle.
N! / (n-k)!

23. a^2 - b^2
.0004809 X 10^11
(a - b)(a + b)
A set with a number of elements which can be counted.
x= (1.2)(.8)lw

24. What is a piecewise equation?
It is a function defined by more than one equation - where each equation applies to a different part of the domain of the function.
1
Even
N! / (k!)(n-k)!

25. What is the slope of a horizontal line?
The sum of its digits is divisible by 3.
0
180 degrees
F(x + c)

26. What is the name for a grouping of the members within a set based on a shared characteristic?
16.6666%
x^(6-3) = x^3
A subset.
From northeast - counterclockwise. I - II - III - IV

27. How to find the area of a sector?
Angle/360 x (pi)r^2
4.25 - 6 - 22
(a - b)(a + b)
Its divisible by 2 and by 3.

28. A number is divisible by 3 if ...
Undefined
Angle/360 x 2(pi)r
The sum of its digits is divisible by 3.
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a

29. Volume for a cylinder?
71 - 73 - 79
Area of the base X height = (pi)hr^2
Its divisible by 2 and by 3.
72

30. Which quadrant is the upper right hand?
1.0843 X 10^11
I
1 & 37/132
A tangent is a line that only touches one point on the circumference of a circle.

31. If you have a set of n objects - but you only want to order k of them - what formula do you use to determine the number of permutations?
N! / (n-k)!
The set of elements found in both A and B.
A central angle is an angle formed by 2 radii.
1

32. Define a 'monomial'
An expression with just one term (-6x - 2a^2)
All numbers multiples of 1.
5 OR -5
A = I (1 + rt)

33. When does a function automatically have a restricted domain (2)?
F(x) + c
When we need to avoid having a zero in the denominator or avoid taking the square root of a number.
...multiply by 100.
True

34. What are the real numbers?
2.592 kg
28. n = 8 - k = 2. n! / k!(n-k)!
16^8 - 64^5 = (4^3)^5 = 4^15 - 16^8=(4^2)^8 = 4^16
All the numbers on the number line (negative - rational - irrational - decimal - integer). All the numbers on the GRE are real. (-2 - 1 - .25 - 1/2 - pi)

35. What is the 'domain' of a function?
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a
The set of input values for a function.
87.5%
12sqrt2

36. a^0 =
3 - -3
A chord is a line segment joining two points on a circle.
1
4sqrt3. The triangle can be divided into two equal 30-60-90 triangles with side 6 as the side in which 6 = xsqrt3. So x =2sqrt3...

37. What is an arc of a circle?
71 - 73 - 79
0
A reflection about the origin.
An arc is a portion of a circumference of a circle.

38. To multiply a number by 10^x
Move the decimal point to the right x places
A circle centered on the origin with radius 8.
F(x) - c
12.5%

39. 3/8 in percent?
55%
90
x^(2(4)) =x^8 = (x^4)^2
37.5%

40. If r - t - s & u are distinct - consecutive prime numbers - less than 31 - which of the following could be an average of them (4 - 4.25 - 6 - 9 - 24 - 22 - 24)
4.25 - 6 - 22
1:1:sqrt2
48
3

41. Which quandrant is the lower right hand?
1
2sqrt6
All numbers multiples of 1.
IV

42. For what values should the domain be restricted for the function f(x) = sqrt(x + 8)
y = 2x^2 - 3
12sqrt2
31 - 37
8

43. What is a parabola?
67 - 71 - 73
3/2 - 5/3
Ax^2 + bx + c where a -b and c are constants and a /=0
(a - b)(a + b)

44. Write 10 -843 X 10^7 in scientific notation
Yes - because you can factor out a perfect square (36). Sqrt(36 x 2) = sqrt36 X sqrt2 = 6sqrt2.
1:sqrt3:2
Expressing a number as the product of a decimal between 1 and 10 - and a power of 10.
1.0843 X 10^11

45. Hector invested $6000. Part was invested in account with 9% simple annual interest - and the rest in account with 7% simple annual interest. If he earned $490 in the first year of these investments - how much did he invest in each account?
$3 -500 in the 9% and $2 -500 in the 7%.
A subset.
A chord is a line segment joining two points on a circle.
6

46. What is the surface area of a cylinder with radius 5 and height 8?
F(x) + c
A set with no members - denoted by a circle with a diagonal through it.
130pi
(a - b)(a + b)

47. Simplify the expression [(b^2 - c^2) / (b - c)]
Angle/360 x 2(pi)r
2.4. We calculate the area (6) and then turn the triangle on its side and use x as the height to calculate again. (5x)/2=6
(b + c)
2

48. How to find the circumference of a circle which circumscribes a square?
9 & 6/7
54sqrt3. (divide the hexagon into 6 congruent equilateral triangles.
Circumference = Diameter(pi). Use pythagorean theorem to find the diagonal of the square (the diameter).
An isosceles right triangle.

49. Whats the difference between factors and multiples?
An infinite set.
Arc length = (n/360) x pi(2r) where n is the number of degrees.
Factors are few - multiples are many.
4096

50. What does the graph (x+2)^2 + (y+2)^2 = 9 look like?
The overlapping sections.
4a^2(b)
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
A circle centered at -2 - -2 with radius 3.