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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. 60 < all primes <70
The set of input values for a function.
x^(2(4)) =x^8 = (x^4)^2
A set with no members - denoted by a circle with a diagonal through it.
61 - 67

2. Employee X is paid 19.50 per hour no matter how many a week. Employee Y earns 18 for the first 40 and 1.5 the hourly wage for every hour after that. If both earned the same amount and worked the same in one week - how many did each work?
6
1
48
1

3. 413.03 x 10^(-4) =
413.03 / 10^4 (move the decimal point 4 places to the left)
9 & 6/7
Indeterminable.
(base*height) / 2

4. What is a tangent?
A circle centered at -2 - -2 with radius 3.
52
0
A tangent is a line that only touches one point on the circumference of a circle.

5. The ratio of the areas of two similar polygons is ...
... the square of the ratios of the corresponding sides.
Its negative reciprocal. (-b/a)
0
F(x-c)

6. a^2 + 2ab + b^2
Move the decimal point to the right x places
12.5%
(a + b)^2
PEMDAS (Parentheses Exponents Multiplication/Division Addition/Subtraction)

7. a^2 - b^2 =
The longest arc between points A and B on a circle'S diameter.
(a - b)(a + b)
(n-2) x 180
1

8. What is the ratio of the surface area of a cube with an edge of 10 to the surface area of a rectangular solid with dimensions 2 - 4 - and 6?
70
75:11
Arc length = (n/360) x pi(2r) where n is the number of degrees.
5 OR -5

9. x^6 / x^3
Its divisible by 2 and by 3.
x^(6-3) = x^3
Two angles whose sum is 90.
Area of the base X height = (pi)hr^2

10. What is the third quartile of the following data set: 44 - 58 - 63 - 63 - 68 - 70 - 82
x^(6-3) = x^3
.0004809 X 10^11
70
1/a^6

11. 25^(1/2) or sqrt. 25 =
5 OR -5
(n-2) x 180
3
90 degrees

12. A number is divisible by 6 if...
Its divisible by 2 and by 3.
Even
All numbers which can be expressed as a ratio of two integers. (All integers and fractions.) (-2 - 1 - .25 - 1/2)
(p + q)/5

13. Define a 'monomial'
An expression with just one term (-6x - 2a^2)
Angle/360 x 2(pi)r
No - the input value has exactly one output.
Part = Percent X Whole

14. What is the name for a grouping of the members within a set based on a shared characteristic?
A subset.
III
A reflection about the origin.
Its negative reciprocal. (-b/a)

15. What is an isoceles triangle?
(n-2) x 180
A set with a number of elements which can be counted.
IV
Two equal sides and two equal angles.

16. 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)
x= (1.2)(.8)lw
IV
x^(4+7) = x^11
4.25 - 6 - 22

17. The perimeter of a square is 48 inches. The length of its diagonal is:
Two angles whose sum is 180.
12sqrt2
x^(2(4)) =x^8 = (x^4)^2
70

18. Factor a^2 + 2ab + b^2
The set of elements which can be found in either A or B.
(a + b)^2
4:5
Factors are few - multiples are many.

19. A triangle is inscribed in a semi circle with legs 5 and 12. What is the circumfermence of the semicircle?
13pi / 2
130pi
5
IV

20. Solve the quadratic equation ax^2 + bx + c= 0
90
The direction of the inequality is reversed.
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a
1

21. What are the rational numbers?
(amount of decrease/original price) x 100%
All numbers which can be expressed as a ratio of two integers. (All integers and fractions.) (-2 - 1 - .25 - 1/2)
180 degrees
Pi is the ratio of a circle'S circumference to its diameter.

22. Factor x^2 - xy + x.
x(x - y + 1)
6
2 & 3/7
83.333%

23. sqrt 2(sqrt 6)=
90pi
Sqrt 12
413.03 / 10^4 (move the decimal point 4 places to the left)
(a - b)(a + b)

24. 2sqrt4 + sqrt4 =
The curve opens downward and the vertex is the maximum point on the graph.
Diameter(Pi)
3sqrt4
An isosceles right triangle.

25. (6sqrt3) x (2sqrt5) =
A reflection about the axis.
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
An arc is a portion of a circumference of a circle.
A subset.

26. How many multiples does a given number have?
27^(-4)
Infinite.
No - the input value has exactly one output.
Expressing a number as the product of a decimal between 1 and 10 - and a power of 10.

27. Describe the relationship between the graphs of x^2 and (1/2)x^2
12.5%
The overlapping sections.
[(7+ sqrt93) /2] - [(7 - sqrt93) / 2]
The second graph is less steep.

28. Suppose you have a set of n objects - and you want to select k of them - but the order doesn'T matter. What formula do you use to determine the number of combinations of n objects taken k at a time?
1:sqrt3:2
16^8 - 64^5 = (4^3)^5 = 4^15 - 16^8=(4^2)^8 = 4^16
The set of input values for a function.
N! / (k!)(n-k)!

29. What is the sum of the angles of a triangle?
The two xes after factoring.
The sum of digits is divisible by 9.
180 degrees
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...

30. Legs 6 - 8. Hypotenuse?
10
3 - -3
2(pi)r^2 + 2(pi)rh
(a - b)(a + b)

31. In a triangle inscribed inside a circle - where the diameter is one side of the triangle - which angle is largest?
Yes. [i.e. f(x) = x^2 - 1
The angle intersecting the circumference is always the largest angle - and is always 90 degrees.
87.5%
(a - b)(a + b)

32. What is a piecewise equation?
(6 x 2)(sqrt3 x sqrt5) = 12sqrt15
12.5%
A = I (1 + rt)
It is a function defined by more than one equation - where each equation applies to a different part of the domain of the function.

33. When does a function automatically have a restricted domain (2)?
(a - b)(a + b)
3/2 - 5/3
When we need to avoid having a zero in the denominator or avoid taking the square root of a number.
16^8 - 64^5 = (4^3)^5 = 4^15 - 16^8=(4^2)^8 = 4^16

34. 50 < all primes< 60
53 - 59
The curve opens downward and the vertex is the maximum point on the graph.
1:1:sqrt2
Cd

35. Evaluate 3& 2/7 / 1/3
61 - 67
9 & 6/7
90
441000 = 1 10 10 10 21 * 21

36. A company places a 6-symbol code on each product. The code consists of the letter T - followed by 3 numerical digits - and then 2 consonants (Y is a conson). How many codes are possible?
441000 = 1 10 10 10 21 * 21
(a + b)^2
1
A central angle is an angle formed by 2 radii.

37. What transformation occurs if point C is reflected over the x-axis and then the y-axis?
A reflection about the axis.
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)
12sqrt2
11 - 13 - 17 - 19

38. What is a parabola?
Sqrt 12
Ax^2 + bx + c where a -b and c are constants and a /=0
1
4096

39. 1:sqrt3:2 is the ratio of the sides of what kind of triangle?
The set of output values for a function.
Angle/360 x (pi)r^2
No - the input value has exactly one output.
A 30-60-90 triangle.

40. What percent of 40 is 22?
Pi is the ratio of a circle'S circumference to its diameter.
The objects within a set.
55%
4:9. The ratio of the areas of two similar triangles equals the square of the ratio of the corresponding sides.

41. What are the real numbers?
180
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)
6
23 - 29

42. What is the set of elements found in both A and B?
The interesection of A and B.
53 - 59
4:9. The ratio of the areas of two similar triangles equals the square of the ratio of the corresponding sides.
x = [(-b)+/- (sqrt b^2 - 4ac)]/2a

43. Formula to find a circle'S circumference from its diameter?
The steeper the slope.
C = 2(pi)r
C = (pi)d
(amount of increase/original price) x 100%

44. What is the percent formula?
Part = Percent X Whole
A reflection about the axis.
II
(base*height) / 2

45. Formula of rectangle where l increases by 20% and w decreases by 20%
Factors are few - multiples are many.
x= (1.2)(.8)lw
(12/2) x (sqrt15 / sqrt5) = 6sqrt3
Use Pythagorean theorem twice. (Once across the surface and then a is the diagonal of surface and b is an edge).

46. 10<all primes<20
23 - 29
11 - 13 - 17 - 19
Indeterminable.
$3 -500 in the 9% and $2 -500 in the 7%.

47. What is the set of elements which can be found in either A or B?
18
A 30-60-90 triangle.
The union of A and B.
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)

48. What is the surface area of a cylinder with radius 5 and height 8?
Yes - like radicals can be added/subtracted.
53 - 59
83.333%
130pi

49. In a regular polygon with n sides - the formula for the sum of interior angles
The set of elements found in both A and B.
Cd
(n-2) x 180
The empty set - denoted by a circle with a diagonal through it.

50. (a^-1)/a^5
Even
1/a^6
Infinite.
$3 -500 in the 9% and $2 -500 in the 7%.